Mountain Weather

Cribyn weather forecast.

795 m summit in Bannau Brycheiniog (Brecon Beacons). 8 forecast days covering wind, cloud, rain and temperature, updated 20 September 2026 at 08:46 UTC.

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Confidence: Medium
Overall hill weather83/100Good
Wind5-25 mph northwesterly Gusts25-35 mph Feels like2 to 6°C PrecipitationLittle or none Cloud-free summit estimate80% Cloud base through day600-1,800 m Freezing levelAbove summit DaylightSunrise 06:55 · Sunset 19:17 · 12.4 hours daylight

The day on the hill

On Cribyn: summit wind broadly 5-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Cloud & views

Cloud layers are possible from about 600-1200 m, with the summit likely to be in cloud. Cloud-height uncertainty could put the summit in or out of cloud.

Clear spells may be difficult to time.

Rain & temperature

Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. Cloud-height uncertainty could put the summit in or out of cloud, even where forecasts agree on the wider cloud cover.

Cloud-free timing: Cloudy early, clearing later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 6.9 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
Less than 1 hour
Midday
3.7 h
Later
2 h

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

Morning · 08:00–12:00 Good Summit winds around 5-25 mph. Gusts around 25-35 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later.
76/100
Afternoon · 12:00–17:00 Excellent Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground.
90/100

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

Overnight · 17:00–08:00Wild campingBetaConditions look exceptional, but forecast uncertainty caps the grade at 97/100. 97/100Excellent · 600 m View detailsHide details
Night beginning Sunday 20 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (97/100). Light winds are expected on open ground, though local shelter and exposure still matter. Little overnight rain is forecast. Forecast models strongly support a good night, but not at the exceptional-certainty threshold. The grade is capped at 97/100.

Overnight rain0.0 mm Open ground · 600 m5 mph · gusts 10 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
70%
Moonrise
17:05 BST
Moonset
00:20 next morning BST

Clear spells may allow a view of the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 20 Sep, 17:00 BST to 21 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m97/100 · very good
Wind / gust
4 mph / 8 mph
Typical / low
10.7°C / 9.4°C · a brief spell
In cloud
0% of modelled night
Condensation
Low
600 m97/100 · very good
Wind / gust
5 mph / 10 mph
Typical / low
10.7°C / 9.4°C · a brief spell
In cloud
0% of modelled night
Condensation
Low

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 6°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock is likely to be mostly dry, but check for local dampness. Excellent86/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look good (86/100). Rock is likely to be mostly dry, though seepage and shaded holds are not resolved. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceProbably dryPeak gust29 mphRain0.0 mm
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaMostly clear skies are forecast. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-20. All times are UK local time.

Stargazing

Very good sky conditions during the best available spell: 21 Sep, 00:00 BST to 01:00 BST.

Mostly clear skies are forecast.

Moon-free dark sky: 21 Sep, 00:15 BST to 05:00 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
20 Sep, 21:10 BST to 22:00 BSTGood sky conditions

Mostly clear skies are forecast.

20 Sep, 22:00 BST to 23:00 BSTGood sky conditions

Mostly clear skies are forecast.

20 Sep, 23:00 BST to 21 Sep, 00:00 BSTVery good sky conditions

Mostly clear skies are forecast.

21 Sep, 00:00 BST to 01:00 BSTVery good sky conditions

Mostly clear skies are forecast.

21 Sep, 01:00 BST to 02:00 BSTVery good sky conditions

Mostly clear skies are forecast.

21 Sep, 02:00 BST to 03:00 BSTMixed sky conditions

Cloud breaks may offer some views of the stars.

21 Sep, 03:00 BST to 04:00 BSTGood sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

21 Sep, 04:00 BST to 05:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

Moon, darkness and meteor showers

Gibbous moon, about 69% illuminated.

Moonrise around 20 Sep, 17:10 BST.

Moonset around 21 Sep, 00:15 BST.

Full darkness: 20 Sep, 21:10 BST to 21 Sep, 05:00 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Sunday 20 September 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

Confidence: Medium
Overall hill weather90/100Excellent
Wind0-10 mph northwesterly Gusts5-15 mph Feels like6 to 10°C PrecipitationLittle or none Cloud-free summit estimate95% Freezing levelAbove summit DaylightSunrise 06:57 · Sunset 19:15 · 12.3 hours daylight

The day on the hill

Little rain and limited summit cloud on Cribyn: summit wind broadly 0-10 mph, with gusts 5-15 mph at times (light winds).

Cloud & views

Cloud base mostly around 1900–2200 m through daylight. The summit is likely to stay mostly clear.

Rain & temperature

Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Forecast models disagree on cloud cover.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.9 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
2.9 h
Midday
4 h
Later
2 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 5-15 mph are possible on exposed ground.
90/100
Afternoon · 12:00–17:00 Excellent Summit winds around 0-10 mph. Gusts around 5-15 mph are possible on exposed ground.
90/100

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

Overnight · 17:00–08:00Wild campingBetaConditions look exceptional, but forecast uncertainty caps the grade at 97/100. 97/100Excellent · 600 m View detailsHide details
Night beginning Monday 21 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (97/100). Light winds are expected on open ground, though local shelter and exposure still matter. Little overnight rain is forecast. Forecast models strongly support a good night, but not at the exceptional-certainty threshold. The grade is capped at 97/100.

Overnight rain0.0 mm Open ground · 600 m3 mph · gusts 9 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 10°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
78%
Moonrise
17:31 BST
Moonset
01:34 next morning BST

Clear spells may allow a view of the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 21 Sep, 17:00 BST to 22 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m97/100 · very good
Wind / gust
2 mph / 7 mph
Typical / low
14.7°C / 12.3°C
In cloud
0% of modelled night
Condensation
Low
600 m97/100 · very good
Wind / gust
3 mph / 9 mph
Typical / low
14.7°C / 12.3°C
In cloud
0% of modelled night
Condensation
Low

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 10°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock is likely to be mostly dry, but check for local dampness. Excellent95/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look excellent (95/100). Rock is likely to be mostly dry, though seepage and shaded holds are not resolved. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceProbably dryPeak gust8 mphRain0.0 mm
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-21. All times are UK local time.

Stargazing

Mixed sky conditions during the best available spell: 22 Sep, 03:00 BST to 04:00 BST.

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Moon-free dark sky: 22 Sep, 01:25 BST to 05:05 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
21 Sep, 21:10 BST to 22:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

21 Sep, 22:00 BST to 23:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

21 Sep, 23:00 BST to 22 Sep, 00:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

22 Sep, 00:00 BST to 01:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

22 Sep, 01:00 BST to 02:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

22 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

22 Sep, 03:00 BST to 04:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

22 Sep, 04:00 BST to 05:00 BSTMixed sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

22 Sep, 05:00 BST to 05:05 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

Moon, darkness and meteor showers

Gibbous moon, about 78% illuminated.

Moonrise around 21 Sep, 17:35 BST.

Moonset around 22 Sep, 01:25 BST.

Full darkness: 21 Sep, 21:10 BST to 22 Sep, 05:05 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Monday 21 September 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

Confidence: Medium
Overall hill weather84/100Good
Possible inversionLow confidence · Morning
Wind0-15 mph southwesterly Gusts10-20 mph Feels like6 to 10°C PrecipitationLittle or none Cloud-free summit estimate90% Cloud base through day800-1,600 m Freezing levelAbove summit DaylightSunrise 06:58 · Sunset 19:12 · 12.2 hours daylight

The day on the hill

Little rain and limited summit cloud on Cribyn: summit wind broadly 0-15 mph, with gusts 10-20 mph at times (light winds). Cloud-height uncertainty could put the summit in or out of cloud.

Clear spells may be difficult to time.

Rain & temperature

Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Cloud-height uncertainty could put the summit in or out of cloud, even where forecasts agree on the wider cloud cover.

Cloud-free timing: Around 70% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 1.8 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
0 h
Midday
1.2 h
Later
Less than 1 hour

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

Morning · 08:00–12:00 Good Summit winds around 5-15 mph. Gusts around 5-15 mph are possible on exposed ground.
78/100
Afternoon · 12:00–17:00 Excellent Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground.
90/100

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

Overnight · 17:00–08:00Wild campingBetaA broadly promising night on a well-chosen pitch. 81/100Good · 600 m View detailsHide details
Night beginning Tuesday 22 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (81/100). It may be breezy on open ground, with gusts near 25 mph. Wind direction may change substantially during the night. Shelter that works at dusk may be less effective later. Little overnight rain is forecast. Some condensation is possible overnight.

Overnight rain0.1 mm Open ground · 600 m10 mph · gusts 26 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
86%
Moonrise
17:50 BST
Moonset
02:51 next morning BST

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: 22 Sep, 17:00 BST to 23 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m86/100 · promising
Wind / gust
8 mph / 22 mph
Typical / low
12.3°C / 10.4°C
In cloud
0% of modelled night
Condensation
Moderate
600 m81/100 · promising
Wind / gust
10 mph / 26 mph
Typical / low
12.3°C / 10.4°C
In cloud
0% of modelled night
Condensation
Moderate

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 8°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock is likely to be mostly dry, but check for local dampness. Excellent95/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look excellent (95/100). Rock is likely to be mostly dry, though seepage and shaded holds are not resolved. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceProbably dryPeak gust14 mphRain0.0 mm
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-22. All times are UK local time.

Stargazing

Poor sky conditions during the best available spell: 23 Sep, 04:00 BST to 05:00 BST.

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Moon-free dark sky: 23 Sep, 02:45 BST to 05:05 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
22 Sep, 21:05 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

22 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

22 Sep, 23:00 BST to 23 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

23 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

23 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud breaks may offer some views of the stars. Reduced visibility may obscure faint objects.

23 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky.

23 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

23 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

23 Sep, 05:00 BST to 05:05 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

Moon, darkness and meteor showers

Gibbous moon, about 85% illuminated.

Moonrise around 22 Sep, 17:50 BST.

Moonset around 23 Sep, 02:45 BST.

Full darkness: 22 Sep, 21:05 BST to 23 Sep, 05:05 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Tuesday 22 September 2026. It asks about intentions, not whether you actually went out. No name or account is needed.

Open the questions to take part.

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Confidence: Medium
Overall hill weather60/100Mixed
Wind15-30 mph northwesterly Gusts30-40 mph Feels like2 to 6°C PrecipitationUp to around 2 mm Cloud-free summit estimate80% Cloud base through day600-1,900 m Freezing levelAbove summit DaylightSunrise 07:00 · Sunset 19:10 · 12.2 hours daylight

The day on the hill

On Cribyn: summit wind broadly 15-30 mph, with gusts 30-40 mph at times (strong winds).

Wind & exposure

Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops.

Cloud & views

Cloud base around 600–900 m in the morning, lifting to 1000–1300 m around midday and 1600–1900 m by late afternoon. Summit cloud is extensive early, becoming less frequent later.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Sunny spells are possible away from summit cloud, but may not reach the top while it is in cloud. Drizzle is forecast at times.

The forecast total is up to around 2 mm, but local amounts will vary. Forecast models differ on summit wind strength: around 18-28 mph at walker height, with gusts 25-40 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. Buffeting may affect balance on exposed ground, particularly near ridges and edges.

Forecast models differ on whether meaningful rain reaches the hills during the morning.

Cloud-free timing: Cloudy early, clearing later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 8.9 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
4 h
Later
2.9 h

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

Morning · 08:00–12:00 Poor Summit winds around 15-30 mph. Gusts around 30-40 mph are possible on exposed ground. Buffeting may affect balance on exposed ground, particularly near ridges and edges. Summit cloud is more persistent early in this period, with better prospects later. Rain is forecast during this period. Rain is possible during the morning, but forecast models disagree on whether it will fall.
45/100
Afternoon · 12:00–17:00 Good Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground. Rain is possible during the afternoon, but forecast models disagree on whether it will fall.
75/100

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

Overnight · 17:00–08:00Wild campingBetaConditions look very good, but forecast uncertainty caps the grade at 88/100. 88/100Excellent · 600 m View detailsHide details
Night beginning Wednesday 23 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (88/100). It may be breezy on open ground, with gusts near 20 mph. Little overnight rain is forecast. Forecast models are not closely enough agreed for an exceptional grade. The grade is capped at 88/100.

Overnight rain0.0 mm Open ground · 600 m9 mph · gusts 22 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 4°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
92%
Moonrise
18:05 BST
Moonset
04:08 next morning BST

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: 23 Sep, 17:00 BST to 24 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m88/100 · very good
Wind / gust
8 mph / 18 mph
Typical / low
8.0°C / 7.6°C · much of the night
In cloud
0% of modelled night
Condensation
Low
600 m88/100 · very good
Wind / gust
9 mph / 22 mph
Typical / low
8.0°C / 7.6°C · much of the night
In cloud
0% of modelled night
Condensation
Low

Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 4°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 35 mph may affect balance on exposed rock. Poor18/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (18/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Gusts may reach about 35 mph. Crosswinds can make exposed ridges substantially more serious.

Rock surfaceWet rock likelyPeak gust36 mphRain0.5 mm
Main factorsgusts around 35 mphwet rock likely
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-23. All times are UK local time.

Stargazing

Poor sky conditions during the best available spell: 23 Sep, 21:05 BST to 22:00 BST.

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Moon-free dark sky: 24 Sep, 04:00 BST to 05:10 BST.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
23 Sep, 21:05 BST to 22:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

23 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.

Forecast models disagree.

23 Sep, 23:00 BST to 24 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky.

24 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects.

24 Sep, 05:00 BST to 05:10 BSTPoor sky conditions

Cloud is likely to obscure much of the sky.

Moon, darkness and meteor showers

Gibbous moon, about 92% illuminated.

Moonrise around 23 Sep, 18:05 BST.

Moonset around 24 Sep, 04:00 BST.

Full darkness: 23 Sep, 21:05 BST to 24 Sep, 05:10 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Wednesday 23 September 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

Confidence: Medium
Overall hill weather88/100Excellent
Wind10-20 mph southerly Gusts20-30 mph Feels like-2 to 2°C PrecipitationLittle or none Cloud-free summit estimate95% Freezing levelAbove summit DaylightSunrise 07:02 · Sunset 19:08 · 12.1 hours daylight

The day on the hill

Little rain and limited summit cloud on Cribyn: summit wind broadly 10-20 mph, with gusts 20-30 mph at times (a moderate breeze).

Cloud & views

Cloud base mostly around 1000–1300 m through daylight. The summit is likely to stay mostly clear.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Cloud height and summit clearance are uncertain. Check again nearer the time.

Keep windproof and warm layers readily available.

Rain & temperature

Little or no rain is forecast. Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around -2 to 2°C in the wind.

Forecast confidence

Forecast models disagree on cloud cover.

Cloud-free timing: Around 95% early, falling to around 85% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.6 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
2 h
Midday
4 h
Later
2.6 h

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

Morning · 08:00–12:00 Excellent Summit winds around 5-15 mph. Gusts around 15-25 mph are possible on exposed ground.
90/100
Afternoon · 12:00–17:00 Excellent Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground.
85/100

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

Overnight · 17:00–08:00Wild campingBetaConditions look very good, but forecast uncertainty caps the grade at 88/100. 88/100Excellent · 600 m View detailsHide details
Night beginning Thursday 24 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (88/100). It may be breezy on open ground, with gusts near 20 mph. Little overnight rain is forecast. Some condensation is possible overnight. Forecast models are not closely enough agreed for an exceptional grade. The grade is capped at 88/100.

Overnight rain0.0 mm Open ground · 600 m13 mph · gusts 20 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
97%
Moonrise
18:17 BST
Moonset
05:26 next morning BST

Clear spells may allow a view of the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 24 Sep, 17:00 BST to 25 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m88/100 · very good
Wind / gust
11 mph / 17 mph
Typical / low
10.5°C / 9.8°C · several hours
In cloud
0% of modelled night
Condensation
Moderate
600 m88/100 · very good
Wind / gust
13 mph / 20 mph
Typical / low
10.5°C / 9.8°C · several hours
In cloud
0% 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 6°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock is likely to be mostly dry, but check for local dampness. Excellent95/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look excellent (95/100). Rock is likely to be mostly dry, though seepage and shaded holds are not resolved. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceProbably dryPeak gust23 mphRain0.0 mm
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-24. All times are UK local time.

Aurora outlook

No significant activity 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: 24 Sep, 21:00 BST to 22:00 BST.

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
24 Sep, 21:00 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

24 Sep, 23:00 BST to 25 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky.

25 Sep, 05:00 BST to 05:10 BSTPoor sky conditions

Cloud is likely to obscure much of the sky.

Moon, darkness and meteor showers

Near-full moon, about 96% illuminated.

Moonrise around 24 Sep, 18:20 BST.

Moonset around 25 Sep, 05:15 BST.

Full darkness: 24 Sep, 21:00 BST to 25 Sep, 05:10 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Thursday 24 September 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

Confidence: Medium
Overall hill weather86/100Excellent
Wind10-25 mph southwesterly Gusts15-25 mph Feels like6 to 10°C PrecipitationLittle or none Cloud-free summit estimate90% Cloud base through day600-1,800 m Freezing levelAbove summit DaylightSunrise 07:03 · Sunset 19:05 · 12.0 hours daylight

The day on the hill

Little rain and limited summit cloud on Cribyn: summit wind broadly 10-25 mph, with gusts 15-25 mph at times (a moderate breeze). Patchy mist is possible in sheltered valleys early on.

Wind & exposure

Much calmer lower down - generally 0-10 mph in the valley, rising towards the tops. Very little direct sunshine is forecast.

Cloud & views

Cloud height and summit clearance are uncertain. Check again nearer the time.

Rain & temperature

Little or no rain is forecast.

Forecast confidence

Forecast models disagree on cloud cover.

Cloud-free timing: Around 40% early, improving to around 95% later.

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 Good Summit winds around 10-20 mph. Gusts around 15-25 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later.
80/100
Afternoon · 12:00–17:00 Excellent Summit winds around 5-15 mph. Gusts around 15-25 mph are possible on exposed ground.
91/100

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

Overnight · 17:00–08:00Wild campingBetaCondensation risk is high near 300 and 600 m. 54/100Mixed · 600 m View detailsHide details
Night beginning Friday 25 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (54/100). Light winds are expected on open ground, though local shelter and exposure still matter. A little rain may coincide with pitching or packing up. Pitches near 600 m may spend part of the night in cloud, bringing damp conditions and poor visibility while cloud is present. Condensation risk is high near 300 and 600 m. Ventilation will matter.

Overnight rain0.4 mm Open ground · 600 m8 mph · gusts 18 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 10°C or lower

Moon overnight

Near-full moon

Illuminated disc
99%
Moonrise
18:29 BST
Moonset
06:45 next morning BST

Cloud at the reference camping height may hide the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 25 Sep, 17:00 BST to 26 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
7 mph / 15 mph
Typical / low
12.6°C / 12.1°C
In cloud
0% of modelled night
Condensation
High
600 m54/100 · mixed
Wind / gust
8 mph / 18 mph
Typical / low
12.6°C / 12.0°C
In cloud
53% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 10°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock is likely to be mostly dry, but check for local dampness. Excellent93/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look excellent (93/100). Rock is likely to be mostly dry, though seepage and shaded holds are not resolved. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceProbably dryPeak gust22 mphRain0.0 mm
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-25. All times are UK local time.

Aurora outlook

No significant activity 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: 25 Sep, 21:00 BST to 22:00 BST.

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
25 Sep, 21:00 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

25 Sep, 23:00 BST to 26 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

26 Sep, 05:00 BST to 05:10 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

Moon, darkness and meteor showers

Near-full moon, about 99% illuminated.

Moonrise around 25 Sep, 18:30 BST.

Moonset around 26 Sep, 06:35 BST.

Full darkness: 25 Sep, 21:00 BST to 26 Sep, 05:10 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Friday 25 September 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

Confidence: Unavailable
Overall hill weather76/100Good
Wind5-20 mph southwesterly Gusts15-25 mph Feels like6 to 10°C PrecipitationUp to around 2 mm Cloud-free summit estimate65% Cloud base through day500-1,700 m Freezing levelAbove summit DaylightSunrise 07:05 · Sunset 19:03 · 12.0 hours daylight

The day on the hill

On Cribyn: summit wind broadly 5-20 mph, with gusts 15-25 mph at times (a moderate breeze).

Cloud & views

Cloud base around 500–800 m in the morning, lifting to 1000–1300 m around midday and 1400–1700 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from around midday into the evening.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Sunny spells are possible away from summit cloud, but may not reach the top while it is in cloud. Drizzle is forecast at times.

The forecast total is up to around 2 mm, but local amounts will vary. Forecast models disagree markedly on summit wind strength.

Check again nearer the time.

Forecast confidence

Overall confidence is unavailable: insufficient comparable wind, rain guidance.

Cloud-free timing: Around 25% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.8 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
2.8 h
Morning · 08:00–12:00 Mixed Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is forecast during this period.
62/100
Afternoon · 12:00–17:00 Excellent Summit winds around 0-15 mph. Gusts around 10-20 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later.
90/100

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

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor45/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (45/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceWet rock likelyPeak gust20 mphRain1.4 mm
Main concernwet rock likely
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. Moonlight washes out fainter stars. View forecastClose forecast

After dark: aurora and stargazing

Night beginning 2026-09-26. All times are UK local time.

Aurora outlook

No significant activity 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: 26 Sep, 20:55 BST to 21:00 BST.

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

A bright Moon remains above the horizon through full darkness, washing out fainter stars and meteors.

Sky conditions through the night
Fully dark periods. Conditions can change between forecast hours.
TimeViewing conditions
26 Sep, 20:55 BST to 21:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

26 Sep, 21:00 BST to 22:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

26 Sep, 22:00 BST to 23:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

26 Sep, 23:00 BST to 27 Sep, 00:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

27 Sep, 00:00 BST to 01:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars.

Limited model coverage.

27 Sep, 01:00 BST to 02:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

Limited model coverage.

27 Sep, 02:00 BST to 03:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

Limited model coverage.

27 Sep, 03:00 BST to 04:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

Limited model coverage.

27 Sep, 04:00 BST to 05:00 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Moonlight washes out fainter stars.

Limited model coverage.

27 Sep, 05:00 BST to 05:15 BSTPoor sky conditions

Cloud is likely to obscure much of the sky. Rain may interrupt viewing. Reduced visibility may obscure faint objects. Moonlight washes out fainter stars.

Limited model coverage.

Moon, darkness and meteor showers

Near-full moon, about 100% illuminated.

Moonrise around 26 Sep, 18:40 BST.

Moonset around 27 Sep, 07:55 BST.

Full darkness: 26 Sep, 20:55 BST to 27 Sep, 05:15 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.

  • Draconids: peak around 9 October 2026.
  • 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 932 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.

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 Cribyn on Saturday 26 September 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

Confidence: Unavailable
Overall hill weather56/100Mixed
Wind15-25 mph southwesterly Gusts25-35 mph Feels like4 to 8°C PrecipitationAround 2-5 mm Cloud-free summit estimate70% Cloud base through day700-1,500 m Freezing levelAbove summit DaylightSunrise 07:07 · Sunset 19:01 · 11.9 hours daylight

The day on the hill

A wet day on Cribyn: summit wind broadly 15-25 mph, with gusts 25-35 mph at times (a fresh breeze). Visibility may drop briefly in showers.

Wind & exposure

Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops.

Cloud & views

Cloud base around 700–1000 m in the morning, then around 1200–1500 m around midday and 1100–1400 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from around midday into the evening.

Cloud-height uncertainty could put the summit in or out of cloud. Clear spells may be difficult to time.

Cloud may hang lower on southwestern slopes and lift somewhat on the northeastern side, but local terrain can differ. Sunny spells are possible away from summit cloud, but may not reach the top while it is in cloud.

Drizzle is forecast for much of the day, with some passing showers too. The forecast total is around 2-5 mm, but local amounts will vary.

Forecast models disagree markedly on summit wind strength. Check again nearer the time.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Overall confidence is unavailable: insufficient comparable wind, rain guidance.

Cloud-free timing: Around 40% early, improving to around 85% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.9 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
2.9 h

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

Morning · 08:00–12:00 Poor Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Rain is forecast during this period.
44/100
Afternoon · 12:00–17:00 Mixed Summit winds around 15-25 mph. Gusts around 25-35 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.
67/100

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

Overnight · 17:00–08:00Wild campingBetaGusts near 30 mph make meaningful shelter important. 59/100Mixed · 600 m View detailsHide details
Night beginning Sunday 27 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (59/100). Open-ground gusts may reach about 30 mph. Seek meaningful shelter. Peak gusts range from about 25 mph at 300 m to 30 mph at 600 m. Around 3.1 mm is forecast, with rain liable to affect both pitching and packing up. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain3.1 mm Open ground · 600 m20 mph · gusts 31 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waning gibbous moon

Illuminated disc
98%
Moonrise
18:53 BST
Moonset
Outside this window

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

Overnight window: 27 Sep, 17:00 BST to 28 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
17 mph / 26 mph
Typical / low
9.2°C / 8.1°C · much of the night
In cloud
0% of modelled night
Condensation
High
600 m59/100 · mixed
Wind / gust
20 mph / 31 mph
Typical / low
9.2°C / 8.1°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 6°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor39/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (39/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Interbedded sandstone and [subequal/subordinate] argillaceous rocks (Brownstones Formation). Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully.

Rock surfaceWet rock likelyPeak gust30 mphRain3.8 mm
Main concernwet rock likely
Mapped rock across the summit and available routes Interbedded sandstone and [subequal/subordinate] argillaceous rocks Brownstones Formation
Origin
Sedimentary
Rock family
Sandstone or gritstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
High confidence
View the summit BGS record

Usually rough and grippy when dry. Damp sandstone and gritstone can feel greasy, and saturated sandstone may be weakened, so let the rock dry fully. Summit-point mapping plus representative BGS bedrock samples along available GPX routes. These are not continuous geological surveys; contacts, superficial deposits and the exposed rock on individual holds may differ.

Rock groups along the sampled routes

These are mapped rock groups, not separate weather forecasts or a ranking of route safety.

Pen Y Fan Horseshoe

sandstone or gritstone

Generic exposed scrambling terrain; mapped summit-point bedrock is 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

A broad surface report is enough; you do not need to identify a particular route.

Overnight · Aurora, stars & meteorsAfter darkBetaNight-sky guidance is unavailable for this night. View forecastClose forecast

After dark: aurora and stargazing

Night-sky guidance is unavailable for this night. This does not mean clear skies or no aurora.

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 Cribyn on Sunday 27 September 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

Weather data: Open-Meteo (CC BY 4.0). Adapted by Mountain Weather.

Forecast run: 2026-09-20

Keep exploring

Weather around Cribyn.

Compare the summit forecast with the wider regional picture and nearby peaks before choosing a route.

Regional mountain forecastBannau Brycheiniog (Brecon Beacons)View area →
Pen y Fan886 m · 1.2 km awayForecast →Waun Rydd769 m · 3.9 km awayForecast →Fan Fawr734 m · 5.7 km awayForecast →Craig Cerrig-gleisiad629 m · 6.3 km awayForecast →

A forecast is part of the decision.

Mountain weather can differ sharply from conditions in the valley. Check official warnings, carry appropriate navigation and clothing, and be ready to change the plan. Read how Mountain Weather forecasts are produced and where their limits lie.

Choose another summit