The day on the hill
A wild day on the tops of Y Garn, with very strong, gusty winds and sleet or snow up high. Not a day for the summit.
Things to watch
Burns could rise quickly through much of the day and into the evening. Timings are rough. Turn back if a crossing looks unsafe.
Wind
On the summit expect a north-westerly wind of around 20–30 mph first thing, rising to 35–45 mph by midday, with gusts of 45–55 mph at the windiest. Lower down on the open hillside it will be more like 15–25 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.
Cloud and visibility
Cloud on the tops early should lift off them by early afternoon. The cloud base could be as low as 300–600 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
Sleet is possible on the tops, and it could turn to snow if it is a little colder. Heavy rain early on, turning lighter by early afternoon. Expect 10–20 mm in total, measured as melted water, so any snow would lie deeper. Totals are uncertain and could be higher.
Warmth and kit
On the tops it will be around 0 to 4°C, feeling like -8 to -4°C in the wind. The freezing level falls through the day, to around 1100–1400 m by midday. Take a hat, gloves, a windproof and a spare warm layer. Pack waterproofs too, and keep a warm layer dry in your pack.
Daylight
Sunset is around 6:05pm, so allow time to get off the hill before dark, and carry a head torch.
Below zero means severe hill conditions. More negative scores indicate more severe forecast weather. Read the hazard details before making plans. Below zero means severe hill conditions. More negative scores indicate more severe forecast weather. Read the hazard details before making plans.
Sunshine context Model-grid estimate, not summit sunshine
The surrounding model grid indicates 1 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
- 0 h
- Later
- 0 h
Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.
Overnight · 17:00–08:00Wild campingBetaToo windy for an exposed pitch above about 600 m (gusts of about 50 mph). Lower down, a poor night to camp on open ground. 19Poor · 600 m View detailsHide details
Full overnight outlook
Too windy for an exposed pitch above about 600 m. Lower down, a poor night to camp on open ground. Gusts reach about 50 mph around 900 m and nearer 35 mph around 300 m, enough to damage a tent on open ground. Pitch low down and in real shelter, or leave it for another night. Dry to pitch, then some light rain overnight and into the morning, so expect to pack a wet tent. Above about 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. A cold night, down to about 2°C around 900 m. A 3-season bag rated to about 2°C comfort, and a warm mat, should do. Allow more if you sleep cold.
Moon overnight
Waxing gibbous moon
- Illuminated disc
- 80%
- Moonrise
- Outside this window
- Moonset
- 03:03 next morning BST
Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.
Overnight window: 21 Oct, 17:00 BST to 22 Oct, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.
Elevation reference (open ground)
- Wind / gust
- 16 mph / 36 mph
- Typical / low
- 5.5°C / 4.9°C · a brief spell
- In cloud
- 0% of modelled night
- Condensation
- Moderate
- Wind / gust
- 19 mph / 43 mph
- Typical / low
- 4.7°C / 4.1°C · much of the night
- In cloud
- 33% of modelled night
- Condensation
- Moderate
- Wind / gust
- 22 mph / 51 mph
- Typical / low
- 2.5°C / 2.0°C · much of the night
- In cloud
- 33% of modelled night
- Condensation
- Moderate
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 & scramblingBetaVery poor conditions for exposed scrambling: gusts of 45–55 mph. Poor0 View detailsHide details
Full climbing & scrambling outlook
Very poor conditions for exposed scrambling. The rock is likely to be wet and slippery through the day. Gusts of 45–55 mph are strong enough to make walking very difficult and tiring, with a risk of being blown off your feet. Avoid exposed ridges and edges. Cloud on the tops may make route-finding and retreat harder. The rock changes around the summit, with mudstone or slate, sandstone and volcanic tuff, so its grip and soundness vary as you go. 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. 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. On the usual routes up you may also cross volcanic tuff, which is rough and grippy when dry and usually still grips reasonably when wet. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.
The rock changes around the summit, with mudstone or slate, sandstone and volcanic tuff, so its grip and soundness vary as you go. The rock changes over short distances here, so check it directly before you commit to a move. Lichen, vegetation and seepage also change how it feels underfoot.
Rock groups along the sampled routes
These are mapped rock groups, not separate weather forecasts or a ranking of route safety.
Elidir Fawr Ridge
volcanic rock, slate or mudstone, sandstone or gritstone
Glyderau Devils Kitchen
volcanic rock, slate or mudstone, sandstone or gritstone
Glyderau Ogwen
slate or mudstone, volcanic rock, sandstone or gritstone
Geological detail and BGS records
14 rock types appear in the mapped samples
No single rock family dominates the summit-area samples, so the forecast uses cautious mixed-rock guidance. The summit pin is shown separately and may not represent nearby crags. Route samples add context where available.
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 recordVolcanic 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 recordMudstone 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 recordVolcanic 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 recordMudstone 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 recordRhyolite is a hard, fine-grained volcanic rock. It grips well when dry and gets slippery on smoother faces when wet. It is hard, but often cracked into sharp, blocky pieces, so some holds are loose.
BGS recordSandstone 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 recordSandstone 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 recordMudstone 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 recordMudstone 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 recordRhyolite is a hard, fine-grained volcanic rock. It grips well when dry and gets slippery on smoother faces when wet. It is hard, but often cracked into sharp, blocky pieces, so some holds are loose.
BGS recordRhyolite is a hard, fine-grained volcanic rock. It grips well when dry and gets slippery on smoother faces when wet. It is hard, but often cracked into sharp, blocky pieces, so some holds are loose.
BGS recordSandstone 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 recordMudstone 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 recordGeneric 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 2026-10-21. All times are UK local time.
Using the last available sky forecast, updated at 06:11 BST on 21 Oct. Cloud conditions may have changed. Live aurora guidance is temporarily unavailable.
Stargazing
Poor sky conditions during the best available spell: 21 Oct, 22:00 BST to 23:00 BST.
Some forecasts show clear spells, others keep it cloudy; check again nearer the time.
Moon-free dark sky: 22 Oct, 03:00 BST to 06:00 BST.
Sky conditions through the night
| Time | Viewing conditions |
|---|---|
| 21 Oct, 20:05 BST to 21:00 BST | Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Moonlight washes out the fainter stars. |
| 21 Oct, 21:00 BST to 22:00 BST | Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree. |
| 21 Oct, 22:00 BST to 23:00 BST | Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree. |
| 21 Oct, 23:00 BST to 22 Oct, 00:00 BST | Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree. |
| 22 Oct, 00:00 BST to 01:00 BST | Poor sky conditions Some forecasts show clear spells, others keep it cloudy; check again nearer the time. Forecast models disagree. |
| 22 Oct, 01:00 BST to 02:00 BST | Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. Moonlight washes out the fainter stars. |
| 22 Oct, 02:00 BST to 03:00 BST | Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. |
| 22 Oct, 03:00 BST to 04:00 BST | Poor sky conditions Mostly cloudy, so little chance of seeing the stars. Rain at times. |
| 22 Oct, 04:00 BST to 05:00 BST | Poor sky conditions Mostly cloudy, so little chance of seeing the stars. |
| 22 Oct, 05:00 BST to 06:00 BST | Poor sky conditions Mostly cloudy, so little chance of seeing the stars. |
Moon, darkness and meteor showers
Gibbous moon, about 80% illuminated.
Moonset around 22 Oct, 03:00 BST.
Full darkness: 21 Oct, 20:05 BST to 22 Oct, 06:00 BST.
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.
Orionids 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.
- Southern Taurids: peak around 10 October 2026.
- Orionids: peak around 21 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 865 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 Y Garn on Wednesday 21 October 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