Gallt yr Ogof Summit Weather Forecast – 763m, Eryri (Snowdonia)

Tuesday 10 November 2026Confidence: Medium

Overall hill weather78Good

Summit wind · 08:00-17:000-10 mph southeasterly Summit gusts · 08:00-17:000-10 mph Feels like0 to 4°C PrecipitationUp to around 2 mm Cloud-free summit estimate85% Freezing levelAbove summit DaylightSunrise 07:29 · Sunset 16:28 · 9.0 hours daylight

The day on the hill

A good day on Gallt yr Ogof: light winds and clear tops for most of the day.

Wind

On the summit expect light winds of up to 5 mph, mainly south-easterly, with gusts of 0–10 mph at the windiest.

Cloud and visibility

The tops are likely to stay mostly clear of cloud, though brief patches cannot be ruled out.

Rain and ground

Drizzle sets in during the early afternoon. The timing could shift by a few hours.

Warmth and kit

On the tops it will be around 2 to 6°C, feeling like 0 to 4°C in the wind. The freezing level is above the summits. Take a warm layer and a hat for the top.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:30pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

Things could still change through the day, so keep an eye on the sky.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 1.6 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 0 h
Midday: 0.8 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Excellent Summit winds around 0-10 mph. Gusts around 0-10 mph are possible on exposed ground. Rain is possible during the morning, but forecast models disagree on whether it will fall. Rain is possible during the main walking period, but its timing may shift by several hours.

85

Afternoon · 12:00–17:00 Good Summit winds around 0-5 mph. Gusts around 0-10 mph are possible on exposed ground. Rain is forecast during this period. Rain is possible during the main walking period, but its timing may shift by several hours.

71

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA mixed night to camp, mainly because of the rain: about 8 mm of rain. 53Mixed · 600 m View detailsHide details

Night beginning Tuesday 10 November 2026

Full overnight outlook

A mixed night to camp, mainly because of the rain. Light winds on open ground, gusting no more than about 15 mph. Expect about 8 mm of rain, mostly early on, so you'll likely pitch in the rain. Up around 600 m you'd likely be in cloud for part of the night: damp, and hard to find your way if you need to move. Overnight lows of about 4°C at 600 m. A warm 3-season or 3–4 season bag rated to about 0°C comfort, and a warm mat, should do. Allow more if you sleep cold.

Overnight rain7.5 mm Open ground · 600 m4 mph · gusts 14 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 0°C or lower

Elevation reference (open ground)

300 m58 · mixed

Wind / gust: 4 mph / 12 mph
Typical / low: 5.3°C / 5.0°C · a brief spell
In cloud: 0% of modelled night
Condensation: High

600 m53 · mixed

Wind / gust: 4 mph / 14 mph
Typical / low: 4.3°C / 3.8°C · much of the night
In cloud: 100% of modelled night
Condensation: High

Warmth planning: As a broad starting point, consider a warm 3-season or 3–4 season bag with an ISO/EN comfort rating at or below about 0°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Daytime · exposed rockClimbing & scramblingBetaPoor conditions for exposed scrambling: wet, slippery rock. Poor28 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Poor conditions for exposed scrambling. The rock is likely to be wet and slippery through the day. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceWet rock likelyPeak gust0-10 mphRain1.7 mm

Main concernwet rock likely

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

Overnight · Aurora, stars & meteorsAfter darkBetaMostly cloudy, so little chance of seeing the stars. Rain at times. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-10. All times are UK local time.

Aurora is unlikely on this night

A noticeable aurora display is unlikely here. Any glow may be faint or camera-only. Activity peaks around Kp 3.0 (on a 0 to 9 scale).

Activity can change at short notice. Check again on the night.

Stargazing

Poor sky conditions during the best available spell: 11 Nov, 03:00 GMT to 04:00 GMT.

Mostly cloudy, so little chance of seeing the stars. Rain at times.

Moon-free dark sky: 10 Nov, 18:30 GMT to 11 Nov, 05:30 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
10 Nov, 18:30 GMT to 19:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
10 Nov, 19:00 GMT to 20:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
10 Nov, 20:00 GMT to 21:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
10 Nov, 21:00 GMT to 22:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
10 Nov, 22:00 GMT to 23:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
10 Nov, 23:00 GMT to 11 Nov, 00:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
11 Nov, 00:00 GMT to 01:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times.
11 Nov, 01:00 GMT to 02:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times.
11 Nov, 02:00 GMT to 03:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times.
11 Nov, 03:00 GMT to 04:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times.
11 Nov, 04:00 GMT to 05:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times.
11 Nov, 05:00 GMT to 05:30 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.

Moon, darkness and meteor showers

Near-new moon, about 3% illuminated.

Full darkness: 10 Nov, 18:30 GMT to 11 Nov, 05:30 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Tuesday 10 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Wednesday 11 November 2026Confidence: Medium

Overall hill weather66Mixed

Summit wind · 08:00-17:000-15 mph easterly Summit gusts · 08:00-17:0010-20 mph Feels like-4 to 0°C PrecipitationLittle or none Cloud-free summit estimate30% Cloud base through day400-1,000 m Freezing levelAbove summit DaylightSunrise 07:31 · Sunset 16:27 · 8.9 hours daylight

The day on the hill

A mixed day on Gallt yr Ogof, with cloud coming and going on the summit.

Wind

On the summit expect light winds of up to 15 mph, mainly easterly, with gusts of 10–20 mph at the windiest.

Cloud and visibility

Expect the summit to be in cloud for most of the day. The cloud base could be as low as 400–700 m early in the morning. In cloud you'll be finding your way without landmarks, so carry navigation you trust and know how to use, with a backup such as a spare battery or a map and compass.

Rain and ground

It should stay dry.

Warmth and kit

On the tops it will be around 0 to 4°C, feeling like -4 to 0°C in the wind. The freezing level is above the summits. Take a hat, gloves, a windproof and a spare warm layer.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:25pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

Cloud height is hard to pin down, so the summit could be in or out of cloud at short notice. Some of the detail could still change, so have a last look at the forecast in the morning before you set off.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 2.6 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Cloud may obscure this summit even while the surrounding model grid indicates sunshine. The low cloud-free summit estimate is a reason to be cautious about expecting views.

Early: 0 h
Midday: 1.6 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Mixed Summit winds around 0-15 mph. Gusts around 10-20 mph are possible on exposed ground.

66

Afternoon · 12:00–17:00 Mixed Summit winds around 0-15 mph. Gusts around 10-20 mph are possible on exposed ground.

66

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA mixed night to camp, mainly because of the cold: gusts of about 20 mph. 59Mixed · 600 m View detailsHide details

Night beginning Wednesday 11 November 2026

Full overnight outlook

A mixed night to camp, mainly because of the cold. Light winds on open ground, gusting no more than about 20 mph. Dry to pitch, then a little rain overnight, easing by morning, though the tent may still be wet. A cold night, down to about 1°C around 600 m. A warm 3-season or 3–4 season bag rated to about -2°C comfort, and a warm mat, should do. Allow more if you sleep cold.

Overnight rain0.5 mm Open ground · 600 m9 mph · gusts 20 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about -2°C or lower

Elevation reference (open ground)

300 m59 · mixed

Wind / gust: 8 mph / 16 mph
Typical / low: 3.9°C / 2.2°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

600 m59 · mixed

Wind / gust: 9 mph / 20 mph
Typical / low: 3.0°C / 1.1°C · much of the night
In cloud: 0% of modelled night
Condensation: Moderate

Warmth planning: As a broad starting point, consider a warm 3-season or 3–4 season bag with an ISO/EN comfort rating at or below about -2°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Daytime · exposed rockClimbing & scramblingBetaMixed conditions for exposed scrambling. Mixed56 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Mixed conditions for exposed scrambling. The rock should be drying, but damp patches, shaded holds and drainage lines may still be wet. Cloud on the tops may make route-finding and retreat harder. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceDamp or dryingPeak gust10-20 mphRainPossible · 22%

Main factorsdamp or incompletely dried rock possiblemuch of the route may be in cloud

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

Overnight · Aurora, stars & meteorsAfter darkBetaSome forecasts show clear spells, others keep it cloudy; check again nearer the time. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-11. All times are UK local time.

Aurora is unlikely on this night

A noticeable aurora display is unlikely here. Any glow may be faint or camera-only. Activity peaks around Kp 3.0 (on a 0 to 9 scale).

Activity can change at short notice. Check again on the night.

Stargazing

Good sky conditions during the best available spell: 12 Nov, 03:00 GMT to 04:00 GMT.

Some forecasts show clear spells, others keep it cloudy; check again nearer the time.

Moon-free dark sky: 11 Nov, 18:25 GMT to 12 Nov, 05:35 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
11 Nov, 18:25 GMT to 19:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
11 Nov, 19:00 GMT to 20:00 GMT	Mixed sky conditions Forecasts disagree about rain or haze, so it could be murkier than this looks. Forecast models disagree.
11 Nov, 20:00 GMT to 21:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
11 Nov, 21:00 GMT to 22:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
11 Nov, 22:00 GMT to 23:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
11 Nov, 23:00 GMT to 12 Nov, 00:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
12 Nov, 00:00 GMT to 01:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
12 Nov, 01:00 GMT to 02:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
12 Nov, 02:00 GMT to 03:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
12 Nov, 03:00 GMT to 04:00 GMT	Good sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 04:00 GMT to 05:00 GMT	Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 05:00 GMT to 05:35 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times.

Moon, darkness and meteor showers

Crescent moon, about 7% illuminated.

Full darkness: 11 Nov, 18:25 GMT to 12 Nov, 05:35 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Wednesday 11 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Thursday 12 November 2026Confidence: High

Overall hill weather87Excellent

Summit wind · 08:00-17:0015-25 mph northerly Summit gusts · 08:00-17:0020-30 mph Feels like-10 to -6°C PrecipitationLittle or none Cloud-free summit estimate90% Freezing level500-800 m DaylightSunrise 07:33 · Sunset 16:25 · 8.9 hours daylight

The day on the hill

A fine day on Gallt yr Ogof: light winds and clear tops for most of the day, though expect snow on the tops.

Snow and navigation

Snow is forecast on the tops in the morning. The air freezing level is roughly 700 to 800 m above sea level. Snow can fall below this, but its lower limit is uncertain.

Wind

On the summit expect a northerly wind of 15–25 mph for most of the day, with gusts of 20–30 mph at the windiest. Lower down on the open hillside it will be more like 5–15 mph. It gets windier still after dark, with summit gusts of 20–30 mph, so bear that in mind if you will be out late.

Cloud and visibility

The tops are likely to stay mostly clear of cloud, though brief patches cannot be ruled out. The air should be clear, so expect far-reaching views as long as the tops stay clear.

Rain and ground

It should stay dry.

Warmth and kit

On the tops it will be around -4 to 0°C, feeling like -10 to -6°C in the wind. The freezing level is close to summit height. Take a hat, gloves, a windproof and a spare warm layer. Pack waterproofs too, and keep a warm layer dry in your pack.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:25pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

It's still two days off, so check again nearer the time.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 7 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 1 h
Midday: 4 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Excellent Summit winds around 15-25 mph. Gusts around 20-30 mph are possible on exposed ground.

88

Afternoon · 12:00–17:00 Excellent Summit winds around 15-25 mph. Gusts around 20-30 mph are possible on exposed ground.

86

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA mixed night to camp, mainly because of the cold: dry, with light winds. 59Mixed · 600 m View detailsHide details

Night beginning Thursday 12 November 2026

Full overnight outlook

A mixed night to camp, mainly because of the cold. Light winds on open ground, gusting no more than about 25 mph. It should stay dry. A cold night, down to about 2°C around 600 m. A warm 3-season or 3–4 season bag rated to about 0°C comfort, and a warm mat, should do. Allow more if you sleep cold.

Overnight rain0.0 mm Open ground · 600 m15 mph · gusts 24 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 0°C or lower

Moon overnight

Waxing crescent moon

Illuminated disc: 13%
Moonrise: Outside this window
Moonset: 17:44 GMT

Views of the Moon may come and go through cloud breaks. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 12 Nov, 17:00 GMT to 13 Nov, 08:00 GMT. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m59 · mixed

Wind / gust: 13 mph / 20 mph
Typical / low: 3.2°C / 3.0°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

600 m59 · mixed

Wind / gust: 15 mph / 24 mph
Typical / low: 2.8°C / 2.1°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

Warmth planning: As a broad starting point, consider a warm 3-season or 3–4 season bag with an ISO/EN comfort rating at or below about 0°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Daytime · exposed rockClimbing & scramblingBetaPoor conditions for exposed scrambling. Poor35 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Poor conditions for exposed scrambling. The rock should be mostly dry, though drainage lines and shaded holds may still be damp. Snow is likely on the rock and ledges, so it becomes a winter route. Gusts of 20–30 mph will be noticeable on exposed ridges. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceProbably dryPeak gust20-30 mphRain0.1 mm

Main concernSnow may fall on high ground. Deposits could make summer scrambling conditions inappropriate

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

Overnight · Aurora, stars & meteorsAfter darkBetaSome forecasts show clear spells, others keep it cloudy; check again nearer the time. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-12. All times are UK local time.

Aurora is unlikely on this night

Too quiet for a likely sighting from here. Activity peaks around Kp 2.0 (on a 0 to 9 scale). It would take about Kp 5.7 for a camera to pick up a glow low in the north, though that is not a hard line.

Activity can change at short notice. Check again on the night.

Stargazing

Mixed sky conditions during the best available spell: 13 Nov, 04:00 GMT to 05:00 GMT.

Some forecasts show clear spells, others keep it cloudy; check again nearer the time.

Moon-free dark sky: 12 Nov, 18:25 GMT to 13 Nov, 05:35 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
12 Nov, 18:25 GMT to 19:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 19:00 GMT to 20:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 20:00 GMT to 21:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 21:00 GMT to 22:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 22:00 GMT to 23:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
12 Nov, 23:00 GMT to 13 Nov, 00:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 00:00 GMT to 01:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 01:00 GMT to 02:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 02:00 GMT to 03:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 03:00 GMT to 04:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 04:00 GMT to 05:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 05:00 GMT to 05:35 GMT	Good sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.

Moon, darkness and meteor showers

Crescent moon, about 13% illuminated.

Moonset around 12 Nov, 17:35 GMT.

Full darkness: 12 Nov, 18:25 GMT to 13 Nov, 05:35 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Thursday 12 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Friday 13 November 2026Confidence: Medium

Overall hill weather92Excellent

Summit wind · 08:00-17:005-20 mph northwesterly Summit gusts · 08:00-17:0020-30 mph Feels like-6 to -2°C PrecipitationUp to around 2 mm Cloud-free summit estimate80% Freezing level700-1,000 m DaylightSunrise 07:35 · Sunset 16:23 · 8.8 hours daylight

The day on the hill

A fine day on Gallt yr Ogof: light winds and clear tops for most of the day, though expect sleet or snow on the tops.

Snow and navigation

Sleet or snow is possible on the tops in the afternoon, with small temperature changes affecting the mix. The air freezing level is roughly 800 to 900 m above sea level. Snow can fall below this, but its lower limit is uncertain.

Wind

On the summit expect a north-westerly wind of 5–20 mph for most of the day, with gusts of 20–30 mph at the windiest.

Cloud and visibility

The tops are likely to stay mostly clear of cloud, though brief patches cannot be ruled out.

Rain and ground

Sleet arrives in the early afternoon. Expect up to 2 mm in total, measured as melted water, so any snow would lie deeper.

Warmth and kit

On the tops it will be around -2 to 2°C, feeling like -6 to -2°C in the wind. The freezing level is close to summit height. Take a hat, gloves, a windproof and a spare warm layer. Pack waterproofs too, and keep a warm layer dry in your pack.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:25pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

Cloud heights are particularly hard to pin down today. It's still three days off and could change, so check again nearer the time.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 5.7 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 2 h
Midday: 2.5 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Excellent Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground.

94

Afternoon · 12:00–17:00 Excellent Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is forecast during this period.

91

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA mixed night to camp, mainly because of the cold: gusts of about 25 mph. 59Mixed · 600 m View detailsHide details

Night beginning Friday 13 November 2026

Full overnight outlook

A mixed night to camp, mainly because of the cold. Gusts reach about 25 mph on open ground, so peg out well and use the guylines. Look for shelter from the northwest. The wind swings from northwesterly to southwesterly overnight, so a pitch sheltered at dusk may not be by morning. It should stay dry. A cold night, down to about 2°C around 300 m. A warm 3-season or 3–4 season bag rated to about 0°C comfort, and a warm mat, should do. Allow more if you sleep cold.

Overnight rain0.0 mm Open ground · 600 m12 mph · gusts 27 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 0°C or lower

Moon overnight

Waxing crescent moon

Illuminated disc: 20%
Moonrise: Outside this window
Moonset: 18:46 GMT

Views of the Moon may come and go through cloud breaks. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 13 Nov, 17:00 GMT to 14 Nov, 08:00 GMT. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m59 · mixed

Wind / gust: 10 mph / 23 mph
Typical / low: 2.9°C / 2.2°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

600 m59 · mixed

Wind / gust: 12 mph / 27 mph
Typical / low: 2.9°C / 2.2°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

Warmth planning: As a broad starting point, consider a warm 3-season or 3–4 season bag with an ISO/EN comfort rating at or below about 0°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Daytime · exposed rockClimbing & scramblingBetaMixed conditions for exposed scrambling: wet, slippery rock. Mixed55 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Mixed conditions for exposed scrambling. The rock is likely to be wet and slippery through the day. Gusts of 20–30 mph will be noticeable on exposed ridges. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceWet rock likelyPeak gust20-30 mphRain0.3 mm

Main concernwet rock likely

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

Overnight · Aurora, stars & meteorsAfter darkBetaSome forecasts show clear spells, others keep it cloudy; check again nearer the time. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-13. All times are UK local time.

Stargazing

Mixed sky conditions during the best available spell: 14 Nov, 00:00 GMT to 01:00 GMT.

Some forecasts show clear spells, others keep it cloudy; check again nearer the time.

Moon-free dark sky: 13 Nov, 18:40 GMT to 14 Nov, 05:35 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
13 Nov, 18:25 GMT to 19:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
13 Nov, 19:00 GMT to 20:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
13 Nov, 20:00 GMT to 21:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
13 Nov, 21:00 GMT to 22:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
13 Nov, 22:00 GMT to 23:00 GMT	Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
13 Nov, 23:00 GMT to 14 Nov, 00:00 GMT	Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
14 Nov, 00:00 GMT to 01:00 GMT	Mixed sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
14 Nov, 01:00 GMT to 02:00 GMT	Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree.
14 Nov, 02:00 GMT to 03:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
14 Nov, 03:00 GMT to 04:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
14 Nov, 04:00 GMT to 05:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
14 Nov, 05:00 GMT to 05:35 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.

Moon, darkness and meteor showers

Crescent moon, about 20% illuminated.

Moonset around 13 Nov, 18:40 GMT.

Full darkness: 13 Nov, 18:25 GMT to 14 Nov, 05:35 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Friday 13 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Saturday 14 November 2026Confidence: Medium

Overall hill weather68Mixed

Summit wind · 08:00-17:0015-30 mph southwesterly Summit gusts · 08:00-17:0030-40 mph Feels like-6 to -2°C PrecipitationUp to around 2 mm Cloud-free summit estimate65% Cloud base through day1,100-1,600 m Freezing levelAbove summit DaylightSunrise 07:37 · Sunset 16:22 · 8.8 hours daylight

The day on the hill

A mixed day on Gallt yr Ogof: breezy on the tops.

Wind

On the summit expect a south-westerly wind of 15–30 mph for most of the day, with gusts of 30–40 mph at the windiest. Lower down on the open hillside it will be more like 5–15 mph. Gusts like that will be noticeable on ridges and open tops, and you will chill quickly when you stop. It gets windier still after dark, with summit gusts of 30–40 mph, so bear that in mind if you will be out late.

Cloud and visibility

The tops are likely to drift in and out of cloud, with the best chance of a clear summit early in the morning. The cloud base could be as low as 500–800 m in the early afternoon. Good spells of sunshine are likely.

Rain and ground

Drizzle sets in around midday.

Warmth and kit

On the tops it will be around 0 to 4°C, feeling like -6 to -2°C in the wind. The freezing level is close to summit height. Take a hat, gloves, a windproof and a spare warm layer. Pack waterproofs too, and keep a warm layer dry in your pack.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:20pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

The forecast models disagree on how strong the wind will be, so it could be noticeably stronger than this. Cloud heights are particularly hard to pin down today. It's still four days off and could change, so check again nearer the time.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 8 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 2 h
Midday: 4 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Good Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Rain is forecast during this period.

77

Afternoon · 12:00–17:00 Mixed Summit winds around 15-30 mph. Gusts around 30-40 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later. Rain is forecast during this period.

60

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaToo windy for an exposed pitch up around 600 m (gusts of about 40 mph and about 4 mm of rain). Lower down, a poor night to camp on open ground. 19Poor · 600 m View detailsHide details

Night beginning Saturday 14 November 2026

Full overnight outlook

Too windy for an exposed pitch up around 600 m. Lower down, a poor night to camp on open ground. Gusts reach about 40 mph on open ground, which makes for a noisy, testing night even in a good tent. Pitch low down and in real shelter, or leave it for another night. Expect about 4 mm of rain, with rain while you pitch and still falling when you pack up. Overnight lows of about 4°C at 600 m. A 3-season bag rated to about 2°C comfort, and a warm mat, should do. Allow more if you sleep cold.

Overnight rain4.5 mm Open ground · 600 m29 mph · gusts 42 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 2°C or lower

Moon overnight

Waxing crescent moon

Illuminated disc: 27%
Moonrise: Outside this window
Moonset: 19:56 GMT

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 14 Nov, 17:00 GMT to 15 Nov, 08:00 GMT. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m39 · poor

Wind / gust: 24 mph / 35 mph
Typical / low: 5.0°C / 4.5°C · several hours
In cloud: 0% of modelled night
Condensation: High

600 m19 · very poor

Wind / gust: 29 mph / 42 mph
Typical / low: 4.7°C / 4.3°C · much of the night
In cloud: 0% of modelled night
Condensation: High

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 2°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Daytime · exposed rockClimbing & scramblingBetaPoor conditions for exposed scrambling: gusts of 30–40 mph. Poor36 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Poor conditions for exposed scrambling. The rock is likely to be wet and slippery through the day. Gusts of 30–40 mph could throw you off balance on exposed moves and ridges. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceWet rock likelyPeak gust30-40 mphRain1.3 mm

Main factorsgusts of 30–40 mphwet rock likely

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

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Overnight · Aurora, stars & meteorsAfter darkBetaMostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-14. All times are UK local time.

Aurora outlook

Nothing notable expected.

A broad activity outlook, not a forecast of a visible display. Cloud and activity can change before the night.

Stargazing

Poor sky conditions during the best available spell: 14 Nov, 20:00 GMT to 21:00 GMT.

Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.

Moon-free dark sky: 14 Nov, 19:50 GMT to 15 Nov, 05:40 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
14 Nov, 18:25 GMT to 19:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
14 Nov, 19:00 GMT to 20:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
14 Nov, 20:00 GMT to 21:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
14 Nov, 21:00 GMT to 22:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars.
14 Nov, 22:00 GMT to 23:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
14 Nov, 23:00 GMT to 15 Nov, 00:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars.
15 Nov, 00:00 GMT to 01:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 01:00 GMT to 02:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 02:00 GMT to 03:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 03:00 GMT to 04:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 04:00 GMT to 05:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 05:00 GMT to 05:40 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.

Moon, darkness and meteor showers

Crescent moon, about 28% illuminated.

Moonset around 14 Nov, 19:50 GMT.

Full darkness: 14 Nov, 18:25 GMT to 15 Nov, 05:40 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Saturday 14 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Sunday 15 November 2026Confidence: Unavailable

Overall hill weather12Poor

Summit wind · 08:00-17:0030-55 mph southwesterly Summit gusts · 08:00-17:0060-70 mph Feels like0 to 4°C PrecipitationAround 5-10 mm Cloud-free summit estimate30% Cloud base through day600-1,500 m Freezing levelAbove summit DaylightSunrise 07:39 · Sunset 16:20 · 8.7 hours daylight

The day on the hill

A poor day on the tops of Gallt yr Ogof, with very strong, gusty winds and burns likely to be in spate.

Things to watch

Burns and rivers are likely to be in spate through the day and overnight, so unbridged crossings could be difficult or impossible. Timings are rough. Turn back if a crossing looks unsafe.

Wind

On the summit expect a south-westerly wind of around 30–40 mph first thing, rising to 45–55 mph by mid-afternoon, with gusts of 60–70 mph at the windiest. Lower down on the open hillside it will be more like 10–20 mph. Gusts like that are strong enough to make walking very difficult and tiring, with a risk of being blown off your feet. Avoid exposed ridges and edges. If the windier forecast models are right, summit gusts could reach 95–105 mph. It gets windier still after dark, with summit gusts of 70–80 mph, so bear that in mind if you will be out late.

Cloud and visibility

Cloud on the tops early should lift off them by early afternoon. The cloud base could be as low as 600–900 m around midday. A few forecast models bring it lower still, to around 400–700 m. In cloud you'll be finding your way without landmarks, so carry navigation you trust and know how to use, with a backup such as a spare battery or a map and compass.

Rain and ground

Rain for much of the day, becoming heavier later. Expect 5–10 mm in total. Some forecast models keep it drier in the morning.

Warmth and kit

On the tops it will be around 6 to 10°C, feeling like 0 to 4°C in the wind. The freezing level is above the summits. A windproof and an extra layer for stops will help. Pack waterproofs too, and keep a warm layer dry in your pack.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:20pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

It's still five days off and could change, so check again nearer the time.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 0 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 0 h
Midday: 0 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Poor Summit winds around 30-40 mph. Gusts around 40-50 mph are possible on exposed ground. Gusts this strong can knock you off balance, so take care near edges and on narrow ridges. Rain is forecast during this period. Some forecast models bring rain during the morning, while others keep it mostly dry.

16

Afternoon · 12:00–17:00 Poor Winds strengthen compared with the morning. More rain is expected. Summit winds around 35-45 mph in the early afternoon, strengthening to 45-55 mph later. Gusts around 60-70 mph are possible on exposed ground. Gusts this strong can make walking very difficult and tiring, with a risk of being blown off your feet. Avoid exposed ridges and edges. Summit cloud is more persistent early in this period, with better prospects later. Rain is forecast during this period. Some forecast models bring rain during the afternoon, while others keep it mostly dry.

8

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaNot a night to camp on the open hill: gusts of about 70 mph and around 16 mm of rain. 0Poor · 600 m View detailsHide details

Night beginning Sunday 15 November 2026

Full overnight outlook

Not a night to camp on the open hill. Gusts reach about 70 mph around 600 m and nearer 55 mph around 300 m, strong enough to flatten or tear a tent. Don't count on finding shelter once you're up there. Choose another night or a low, sheltered spot. Expect a wet night, around 16 mm of rain, mostly early on, so you'll likely pitch in the rain. A cold night, down to about 2°C around 300 m. A warm 3-season or 3–4 season bag rated to about 0°C comfort, and a warm mat, should do. Allow more if you sleep cold.

Overnight rain16.1 mm Open ground · 600 m33 mph · gusts 69 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 0°C or lower

Moon overnight

Waxing crescent moon

Illuminated disc: 36%
Moonrise: Outside this window
Moonset: 21:10 GMT

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 15 Nov, 17:00 GMT to 16 Nov, 08:00 GMT. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m9 · very poor

Wind / gust: 28 mph / 57 mph
Typical / low: 10.2°C / 1.9°C · several hours
In cloud: 0% of modelled night
Condensation: Moderate

600 m0 · very poor

Wind / gust: 33 mph / 69 mph
Typical / low: 6.2°C / 1.9°C · several hours
In cloud: 0% of modelled night
Condensation: Moderate

Warmth planning: As a broad starting point, consider a warm 3-season or 3–4 season bag with an ISO/EN comfort rating at or below about 0°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

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Daytime · exposed rockClimbing & scramblingBetaVery poor conditions for exposed scrambling: gusts of 60–70 mph. Poor0 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Very poor conditions for exposed scrambling. The rock is likely to be wet and slippery through the day. Gusts of 60–70 mph are strong enough to make movement extremely difficult on exposed ground. During the strongest gusts, walking or standing may be impossible and you could be blown off your feet. Avoid exposed high ground. Cloud on the tops may make route-finding and retreat harder. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceWet rock likelyPeak gust60-70 mphRain10.9 mm

Main factorsgusts of 60–70 mphwet rock likelymuch of the route may be in cloud

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

Overnight · Aurora, stars & meteorsAfter darkBetaMostly cloudy, so little chance of seeing the stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-15. All times are UK local time.

Aurora outlook

Nothing notable expected.

A broad activity outlook, not a forecast of a visible display. Cloud and activity can change before the night.

Stargazing

Mixed sky conditions during the best available spell: 16 Nov, 04:00 GMT to 05:00 GMT.

Mostly cloudy, so little chance of seeing the stars.

Moon-free dark sky: 15 Nov, 21:10 GMT to 16 Nov, 05:40 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
15 Nov, 18:20 GMT to 19:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 19:00 GMT to 20:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 20:00 GMT to 21:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 21:00 GMT to 22:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 22:00 GMT to 23:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
15 Nov, 23:00 GMT to 16 Nov, 00:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars.
16 Nov, 00:00 GMT to 01:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars. Limited model coverage.
16 Nov, 01:00 GMT to 02:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 02:00 GMT to 03:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 03:00 GMT to 04:00 GMT	Mixed sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 04:00 GMT to 05:00 GMT	Mixed sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 05:00 GMT to 05:40 GMT	Good sky conditions Some breaks in the cloud, so stars at times. Limited model coverage.

Moon, darkness and meteor showers

Crescent moon, about 36% illuminated.

Moonset around 15 Nov, 21:10 GMT.

Full darkness: 15 Nov, 18:20 GMT to 16 Nov, 05:40 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

Does the weather shape your plans?Optional hill-user research. One answer helps; further questions are up to you.Take part

Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Sunday 15 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

About the research and your privacy · Already been out? Share that experience instead

Monday 16 November 2026Confidence: Unavailable

Overall hill weather96Excellent

Summit wind · 08:00-17:005-20 mph westerly Summit gusts · 08:00-17:0015-25 mph Feels like-6 to -2°C PrecipitationLittle or none Cloud-free summit estimate90% Freezing level700-1,000 m DaylightSunrise 07:41 · Sunset 16:19 · 8.6 hours daylight

The day on the hill

A fine day on Gallt yr Ogof: dry, with light winds and clear tops for most of the day.

Wind

On the summit expect a westerly wind of 5–20 mph for most of the day, with gusts of 15–25 mph at the windiest. Lower down on the open hillside the wind will be light, under 10 mph.

Cloud and visibility

The tops are likely to stay mostly clear of cloud, though brief patches cannot be ruled out. The air should be clear, so expect far-reaching views as long as the tops stay clear.

Rain and ground

It should stay dry. Some forecast models bring rain, so don't count on it staying dry. The ground is very wet after recent rain, so expect boggy paths.

Warmth and kit

On the tops it will be around 0 to 4°C, feeling like -6 to -2°C in the wind. The freezing level is close to summit height. Take a hat, gloves, a windproof and a spare warm layer.

Daylight

A short day, with only about 9 hours of daylight. Sunset is around 4:20pm, so allow time to get off the hill before dark, and carry a head torch.

Forecast confidence

It's still six days off and could change, so check again nearer the time.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 8 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 2 h
Midday: 4 h
Later: 0 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Excellent Summit winds around 10-20 mph. Gusts around 15-25 mph are possible on exposed ground.

95

Afternoon · 12:00–17:00 Excellent Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground.

96

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaNot a night to camp on the open hill: gusts of about 50 mph and around 13 mm of rain. 9Poor · 600 m View detailsHide details

Night beginning Monday 16 November 2026

Full overnight outlook

Not a night to camp on the open hill. Gusts reach about 50 mph on open ground, enough to damage a tent on open ground. Don't count on finding shelter once you're up there. Choose another night or a low, sheltered spot. The wind swings from southerly to westerly overnight, so a pitch sheltered at dusk may not be by morning. Expect a wet night, around 13 mm of rain, with rain while you pitch and still falling when you pack up. Up around 600 m you'd likely be in cloud for part of the night: damp, and hard to find your way if you need to move. Overnight lows of about 4°C at 300 m. A 3-season bag rated to about 2°C comfort, and a warm mat, should do. Allow more if you sleep cold. The ground will be sodden after recent rain, so pick a firm, well-drained pitch.

Overnight rain12.6 mm Open ground · 600 m17 mph · gusts 48 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 2°C or lower

Moon overnight

First-quarter moon

Illuminated disc: 46%
Moonrise: Outside this window
Moonset: 22:26 GMT

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 16 Nov, 17:00 GMT to 17 Nov, 08:00 GMT. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m19 · very poor

Wind / gust: 14 mph / 40 mph
Typical / low: 8.4°C / 4.0°C · a brief spell
In cloud: 0% of modelled night
Condensation: High

600 m9 · very poor

Wind / gust: 17 mph / 48 mph
Typical / low: 7.9°C / 4.0°C · a brief spell
In cloud: 40% of modelled night
Condensation: High

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 2°C. Allow more margin if you sleep cold or expect fatigue, and use an adequate insulated mat. Dampness is possible, so keep the sleep system dry and ensure its insulation remains effective if damp.

The ground is likely to be very wet after recent rain. Expect boggy approaches and choose a durable pitch carefully.

Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Daytime · exposed rockClimbing & scramblingBetaGood conditions for exposed scrambling. Good75 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Good conditions for exposed scrambling. After recent rain the rock may still be wet in places, especially shaded holds and drainage lines. The rock around the summit is mostly mudstone or slate, a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.

Rock surfaceDry overhead; seepage uncertainPeak gust15-25 mphRain0.1 mm

Main concerndamp or incompletely dried rock possible

Most common mapped rock around the summit Siltstone Capel Curig Volcanic Formation

Origin: Sedimentary
Broad rock-response group: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Summit area: Slate or mudstone in 53% of 17 BGS samples within 350 m
Summit pin: Microgabbro (Unnamed Igneous Intrusion, Ordovician)
Rock-response profile: Moderate confidence

View the summit BGS record

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. These are general notes for each rock type, from geological map samples at and around the summit. The rock on your line can differ, and lichen, vegetation and seepage all change how it feels underfoot.

Geological detail and BGS records

Mapped variation

5 rock types appear in the mapped samples

Samples around the summit inform the main rock-response profile, with the summit pin shown separately where it differs. Route samples add further context, but this is not a continuous geological survey.

Summit-area sample Microgabbro Unnamed Igneous Intrusion, Ordovician

Dolerite is a hard, dark, fine-grained rock. It grips well when dry and is fair when wet. It is usually solid, but it often breaks into blocky columns, so check blocks before you pull on them.

BGS record

Summit-area sample Siltstone Capel Curig Volcanic Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Felsic tuff Capel Curig Volcanic Formation

Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.

BGS record

Summit-area sample Mudstone and siltstone Cwm Eigiau Formation

Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.

BGS record

Summit-area sample Sandstone Llewelyn Volcanic Group

Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.

BGS record

Generic exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.

Did this match your experience?Tell us about the rock surface and wind to help improve this beta forecast.Give feedback

Overnight · Aurora, stars & meteorsAfter darkBetaMostly cloudy, so little chance of seeing the stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-11-16. All times are UK local time.

Aurora outlook

Nothing notable expected.

A broad activity outlook, not a forecast of a visible display. Cloud and activity can change before the night.

Stargazing

Poor sky conditions during the best available spell: 16 Nov, 19:00 GMT to 20:00 GMT.

Mostly cloudy, so little chance of seeing the stars.

Moon-free dark sky: 16 Nov, 22:25 GMT to 17 Nov, 05:40 GMT.

Sky conditions through the night

Fully dark periods. Conditions can change between forecast hours.
Time	Viewing conditions
16 Nov, 18:20 GMT to 19:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 19:00 GMT to 20:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 20:00 GMT to 21:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 21:00 GMT to 22:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 22:00 GMT to 23:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Limited model coverage.
16 Nov, 23:00 GMT to 17 Nov, 00:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Hazy, which dims the fainter stars. Limited model coverage.
17 Nov, 00:00 GMT to 01:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars. Limited model coverage.
17 Nov, 01:00 GMT to 02:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars. Limited model coverage.
17 Nov, 02:00 GMT to 03:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars. Limited model coverage.
17 Nov, 03:00 GMT to 04:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars. Limited model coverage.
17 Nov, 04:00 GMT to 05:00 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars. Limited model coverage.
17 Nov, 05:00 GMT to 05:40 GMT	Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Hazy, which dims the fainter stars. Limited model coverage.

Moon, darkness and meteor showers

Around half moon, about 46% illuminated.

Moonset around 16 Nov, 22:25 GMT.

Full darkness: 16 Nov, 18:20 GMT to 17 Nov, 05:40 GMT.

Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.

Southern Taurids are active on this night. Activity may be much lower away from the peak.

Northern Taurids are active on this night. Activity may be much lower away from the peak.

Leonids are active on this night. Activity may be much lower away from the peak.

Southern Taurids: peak around 10 October 2026.
Northern Taurids: peak around 12 November 2026.
Leonids: peak around 18 November 2026.
Geminids: peak around 14 December 2026.
Ursids: peak around 22 December 2026.

Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.

Darkness of the surroundings

Estimated darkness rank 820 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.

2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.

VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.

Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.

Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.

Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit

For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.

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Help the Mountain Decisions Project understand how forecasts influence hill days, including when plans stay the same. Findings will be shared publicly as summaries, not individual responses.

This is about Gallt yr Ogof on Monday 16 November 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

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Gallt yr Ogof weather forecast.

Choose your hill day.

The day on the hill

Wind

Cloud and visibility

Rain and ground

Warmth and kit

Daylight

Forecast confidence

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear in the mapped samples

After dark: aurora and stargazing

Aurora is unlikely on this night

Stargazing

Darkness of the surroundings

The day on the hill

Wind

Cloud and visibility

Rain and ground

Warmth and kit

Daylight

Forecast confidence

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear in the mapped samples

After dark: aurora and stargazing

Aurora is unlikely on this night

Stargazing

Darkness of the surroundings

The day on the hill

Snow and navigation

Wind

Cloud and visibility

Rain and ground

Warmth and kit

Daylight

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear in the mapped samples

After dark: aurora and stargazing

Aurora is unlikely on this night

Stargazing

Darkness of the surroundings

The day on the hill

Snow and navigation

Wind

Cloud and visibility

Rain and ground

Warmth and kit

Daylight

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear in the mapped samples

After dark: aurora and stargazing

Stargazing

Darkness of the surroundings

The day on the hill

Wind

Cloud and visibility

Rain and ground

Warmth and kit

Daylight

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear in the mapped samples

After dark: aurora and stargazing

Aurora outlook

Stargazing