Pen yr Ole Wen Weather Forecast – 978m, Eryri (Snowdonia)

Friday 4 September 2026Medium confidence

Overall hill weather26/100Poor

Wind33 mph W Gusts46 mph Feels2°C Rain0.3 mm Cloud-free summit30% Cloud base through day500–1,300 m Freezing levelAbove summit Daylight06:30–19:59 · 13.5 h

Forecast confidence: Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud.

Severe spate risk

Burns and unbridged crossings may rise quickly. Assess them at the water and turn back if unsure.

Cloud-free timing: Around 45% early, falling to around 25% later.

A wild day on Pen yr Ole Wen: summit wind broadly 25-40 mph, with gusts 40-50 mph during the morning (gale-force winds). Severe spate risk based on forecast rainfall. Burns and unbridged crossings may become unsafe or impassable. Most likely from around 00:00 until around 13:00. Cloud base around 1000–1300 m in the morning, then around 500–800 m around midday and 1000–1300 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view during the morning. Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. Sunshine is likely to be limited to about 1 hour through breaks in the cloud. Little or no rain expected. Cold on top: air temperature broadly 6 to 10°C, feeling around 0 to 4°C in the wind - wrap up. Confidence moderate (forecast models agree on the walking impact of the wind) - walker-height summit wind could reasonably be 29-36 mph, with gusts 41-51 mph. Cloud base is the least certain part of this - it could sit a couple of hundred metres either way, especially where it is close to summit level.

At this mountain

Sunshine and sky

Limited sunny breaks. Any sunshine is likely to come through limited breaks.

Modelled sunshine1.4 h11% of daylight

Early0 h sunshine

MiddayLess than 1 hour sunshine

Later1.2 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Poor

22/100

Afternoon & evening · 13:00–22:00Poor

30/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 45 mph make meaningful shelter important. 64/100Mixed · 600 m View detailsHide details

Night beginning Friday 4 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). A lower pitch near 300 m looks more comfortable; conditions are less suitable by 900 m. Open-ground gusts may reach about 45 mph, making exposed pitches a poor choice. Peak gusts increase from about 30 mph at 300 m to 45 mph at 900 m. Little overnight rain is expected. From around 600 m upward, pitches may spend part of the night in cloud, with high condensation risk, persistent damp and poor visibility; ventilation will matter. The coldest temperature falls from about 8.5°C at 300 m to 6.7°C at 900 m.

Overnight rain0.0 mm Open ground · 600 m23 mph · gusts 39 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m64/100 · reasonable

Wind / gust: 19 / 32 mph
Typical / low: 9.3° / 8.5°C · much of the night
In cloud: Unlikely
Condensation: High

600 m64/100 · reasonable

Wind / gust: 23 / 39 mph
Typical / low: 9.2° / 8.5°C · much of the night
In cloud: 31% of night
Condensation: High

900 m39/100 · poor

Wind / gust: 27 / 46 mph
Typical / low: 7.3° / 6.7°C · much of the night
In cloud: 31% of 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

Daytime · exposed rockClimbing & scramblingBetaGusts near 45 mph increase the seriousness of exposed ground. 0/100Poor · Very poor View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (0/100). Rain during the useful part of the day is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 45 mph; crosswinds can make exposed ridges substantially more serious.

Rock surfaceWet rock likelyPeak gust46 mphRain0.2 mm

Main factorsgusts around 45 mphwet rock likely

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Friday 4 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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Saturday 5 September 2026Medium confidence

Overall hill weather80/100Good

Wind23 mph W Gusts32 mph Feels2°C Rain0.0 mm Cloud-free summit45% Cloud base through day1,000–1,300 m Freezing levelAbove summit Daylight06:31–19:56 · 13.4 h

Forecast confidence: Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud.

Cloud-free timing: Around 55% early, falling to around 45% later.

A mixed day on Pen yr Ole Wen: summit wind broadly 10-30 mph, with gusts 25-35 mph early in the morning (strong winds). The ground is likely to be saturated after recent rain. Expect boggy paths and rapid runoff if more rain arrives. Cloud base mostly around 1000–1300 m through daylight. The top is likely to drift in and out of cloud, with the best chance of a view from midday into the afternoon. Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud. about 5 hours of sunshine is indicated, with cloud tending to break and brighter spells becoming more likely later. Little or no rain expected. Cold on top: air temperature broadly 4 to 8°C, feeling around 0 to 4°C in the wind - wrap up. Confidence moderate (forecast models agree on the walking impact of the wind) - walker-height summit wind could reasonably be 21-25 mph, with gusts 29-36 mph. Cloud base is the least certain part of this - it could sit a couple of hundred metres either way, especially where it is close to summit level.

At this mountain

Sunshine and sky

Cloud breaking up. Brighter spells should become more frequent as cloud breaks.

Modelled sunshine5.4 h42% of daylight

Early0 h sunshine

Midday2.1 h sunshine

Later2.3 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Mixed

69/100

Afternoon & evening · 13:00–22:00Excellent

92/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 35 mph make meaningful shelter important. 86/100Excellent · 600 m View detailsHide details

Night beginning Saturday 5 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (86/100). Open-ground gusts may reach about 35 mph; seek meaningful shelter. Peak gusts increase from about 25 mph at 300 m to 35 mph at 900 m. Little overnight rain is expected. From around 900 m upward, pitches may spend part of the night in cloud, bringing persistent damp and poor visibility. The coldest temperature falls from about 9.8°C at 300 m to 7.8°C at 900 m.

Overnight rain0.2 mm Open ground · 600 m13 mph · gusts 27 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m88/100 · very good

Wind / gust: 11 / 23 mph
Typical / low: 12.5° / 9.8°C · a brief spell
In cloud: Unlikely
Condensation: Moderate

600 m86/100 · promising

Wind / gust: 13 / 27 mph
Typical / low: 12.5° / 9.8°C · a brief spell
In cloud: Unlikely
Condensation: Moderate

900 m79/100 · promising

Wind / gust: 16 / 37 mph
Typical / low: 10.2° / 7.8°C · several hours
In cloud: 31% of 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.

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

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

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

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying after recent rain. 65/100Mixed · Fair View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (65/100). Some rock may still be damp or drying; polished slabs and vegetated sections could be notably worse. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain.

Rock surfaceDamp or dryingPeak gust28 mphRain0.0 mm

Main concerndamp or incompletely dried rock possible

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Saturday 5 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

Sunday 6 September 2026Medium confidence

Overall hill weather44/100Poor

Wind36 mph SW Gusts50 mph Feels9°C Rain0.3 mm Cloud-free summit55% Cloud base through day600–2,000 m Freezing levelAbove summit Daylight06:33–19:54 · 13.3 h

Forecast confidence: Rain timing may shift by several hours, which could change how much of the main walking period stays dry.

Cloud-free timing: Best around midday at about 70%; around 45% early and 40% later.

A wild day on Pen yr Ole Wen: summit wind broadly 25-40 mph, with gusts 45-55 mph around midday (gale-force winds). The ground is likely to be wet after recent rain. Much calmer lower down - generally 15-25 mph in the valley, rising towards the tops. Cloud base around 600–900 m in the morning, then around 1700–2000 m around midday and 700–1000 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from the morning into the afternoon. Cloud is likely to hang lowest on southwestern slopes; the northeastern side should see somewhat higher bases and better breaks. about 8 hours of sunshine is indicated, with variable cloud giving brighter and duller spells. Little or no rain expected. Confidence moderate (forecast models agree on the walking impact of the wind) - walker-height summit wind could reasonably be 31-41 mph, with gusts 43-57 mph.

At this mountain

Sunshine and sky

Brighter and duller spells. Expect alternating brighter and duller spells.

Modelled sunshine8.4 h65% of daylight

Early0 h sunshine

Midday4 h sunshine

Later2.8 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Poor

44/100

Afternoon & evening · 13:00–22:00Poor

44/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 45 mph make meaningful shelter important. 54/100Mixed · 600 m View detailsHide details

Night beginning Sunday 6 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (54/100). A lower pitch near 300 m looks more comfortable; conditions are less suitable by 900 m. Open-ground gusts may reach about 45 mph, making exposed pitches a poor choice. Peak gusts increase from about 30 mph at 300 m to 45 mph at 900 m. Around 2.4 mm is forecast, with a damp or wet pitch most likely. From around 600 m upward, pitches may spend part of the night in cloud, with high condensation risk, persistent damp and poor visibility; ventilation will matter. The coldest temperature falls from about 10.2°C at 300 m to 7.8°C at 900 m.

Overnight rain2.4 mm Open ground · 600 m22 mph · gusts 38 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m75/100 · promising

Wind / gust: 18 / 32 mph
Typical / low: 14.2° / 10.2°C
In cloud: Unlikely
Condensation: Moderate

600 m54/100 · mixed

Wind / gust: 22 / 38 mph
Typical / low: 14.0° / 9.9°C · a brief spell
In cloud: 69% of night
Condensation: High

900 m39/100 · poor

Wind / gust: 26 / 45 mph
Typical / low: 12.2° / 7.8°C · several hours
In cloud: 69% of 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

Daytime · exposed rockClimbing & scramblingBetaGusts near 50 mph increase the seriousness of exposed ground. 0/100Poor · Very poor View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (0/100). Rain during the useful part of the day is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 50 mph; crosswinds can make exposed ridges substantially more serious.

Rock surfaceWet rock likelyPeak gust50 mphRain0.3 mm

Main factorsgusts around 50 mphwet rock likely

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Sunday 6 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

Monday 7 September 2026Medium confidence

Overall hill weather63/100Mixed

Wind26 mph W Gusts37 mph Feels2°C Rain0.0 mm Cloud-free summit50% Cloud base through day1,200–2,200 m Freezing levelAbove summit Daylight06:35–19:51 · 13.3 h

Forecast confidence: Rain could reach the main walking period or hold off until later; forecast models disagree on the timing.

Cloud-free timing: Around 45% early, improving to around 55% later.

A mixed day on Pen yr Ole Wen: summit wind broadly 15-30 mph, with gusts 30-40 mph during the evening (strong winds). The ground is likely to be wet after recent rain. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. about 7 hours of sunshine is indicated, with variable cloud giving brighter and duller spells. Little or no rain expected. Confidence moderate (forecast models agree on the walking impact of the wind) - walker-height summit wind could reasonably be 23-29 mph, with gusts 32-41 mph. Cloud base is the least certain part of this - it could sit a couple of hundred metres either way, especially where it is close to summit level.

At this mountain

Sunshine and sky

Brighter and duller spells. Expect alternating brighter and duller spells.

Modelled sunshine6.6 h50% of daylight

Early1.8 h sunshine

Midday1 h sunshine

Later2.7 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Mixed

58/100

Afternoon & evening · 13:00–22:00Mixed

68/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 50 mph make meaningful shelter important. 67/100Mixed · 600 m View detailsHide details

Night beginning Monday 7 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (67/100). A lower pitch near 300 m looks more comfortable; conditions are less suitable by 900 m. Open-ground gusts may reach about 50 mph, making exposed pitches a poor choice. Peak gusts increase from about 35 mph at 300 m to 50 mph at 900 m. Wind may shift from southwesterly to northwesterly; shelter that works at dusk may be less effective later. Around 1.2 mm is forecast, with a damp or wet pack-up most likely. From around 600 m upward, pitches may spend part of the night in cloud, bringing persistent damp and poor visibility. The coldest temperature falls from about 9.3°C at 300 m to 6.2°C at 900 m.

Overnight rain1.2 mm Open ground · 600 m21 mph · gusts 43 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m75/100 · promising

Wind / gust: 18 / 36 mph
Typical / low: 10.5° / 9.3°C · a brief spell
In cloud: Unlikely
Condensation: Moderate

600 m67/100 · reasonable

Wind / gust: 21 / 43 mph
Typical / low: 9.7° / 8.4°C · much of the night
In cloud: 44% of night
Condensation: Moderate

900 m39/100 · poor

Wind / gust: 25 / 50 mph
Typical / low: 7.9° / 6.2°C · much of the night
In cloud: 50% of 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

Daytime · exposed rockClimbing & scramblingBetaGusts near 35 mph increase the seriousness of exposed ground. 20/100Poor · Poor View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (20/100). It may be dry overhead, but recent rain leaves uncertainty around seepage and shaded sections. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 35 mph; crosswinds can make exposed ridges substantially more serious.

Rock surfaceDry overhead; seepage uncertainPeak gust34 mphRainPossible · 98%

Main factorsgusts around 35 mphdamp or incompletely dried rock possible

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Monday 7 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

Tuesday 8 September 2026Medium confidence

Overall hill weather42/100Poor

Wind27 mph NW Gusts38 mph Feels-1°C Rain2.7 mm Cloud-free summit25% Cloud base through day400–1,200 m Freezing levelAbove summit Daylight06:37–19:49 · 13.2 h

Forecast confidence: Rain could reach the main walking period or hold off until later; forecast models disagree on the timing.

Cloud-free timing: Around 15% early, improving to around 55% later.

A grey, cloudy day on Pen yr Ole Wen: summit wind broadly 15-30 mph, with gusts 35-45 mph during the evening (strong winds). Cloud base around 400–700 m in the morning, lifting to 500–800 m around midday and 900–1200 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from late afternoon into the evening. Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud. Cloud is likely to hang lowest on northwestern slopes; the southeastern side should see somewhat higher bases and better breaks. about 12 hours of sunshine is indicated, with cloud tending to break and brighter spells becoming more likely later. Some rain is likely, with around 2-5 mm indicated; timing and local totals remain uncertain. Cold on top: air temperature broadly 2 to 6°C, feeling around -4 to 0°C in the wind - wrap up. Confidence moderate (forecast models agree on the walking impact of the wind) - walker-height summit wind could reasonably be 23-31 mph, with gusts 33-43 mph. Cloud base is the least certain part of this - it could sit a couple of hundred metres either way, especially where it is close to summit level.

At this mountain

Sunshine and sky

Cloud breaking up. Brighter spells should become more frequent as cloud breaks.

Modelled sunshine12 h92% of daylight

Early2 h sunshine

Midday4 h sunshine

Later4 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Poor

37/100

Afternoon & evening · 13:00–22:00Poor

47/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 40 mph make meaningful shelter important. 67/100Mixed · 600 m View detailsHide details

Night beginning Tuesday 8 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (67/100). A lower pitch near 300 m looks more comfortable; conditions are less suitable by 900 m. Open-ground gusts may reach about 40 mph; seek meaningful shelter. Peak gusts increase from about 30 mph at 300 m to 40 mph at 900 m. Around 4.5 mm is forecast, with a damp or wet pack-up most likely. From around 600 m upward, pitches may spend part of the night in cloud, with high condensation risk, persistent damp and poor visibility; ventilation will matter. The coldest temperature falls from about 8.1°C at 300 m to 5.5°C at 900 m.

Overnight rain4.5 mm Open ground · 600 m17 mph · gusts 33 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m70/100 · reasonable

Wind / gust: 14 / 28 mph
Typical / low: 8.2° / 8.1°C · much of the night
In cloud: Unlikely
Condensation: Moderate

600 m67/100 · reasonable

Wind / gust: 17 / 33 mph
Typical / low: 8.2° / 8.0°C · much of the night
In cloud: 38% of night
Condensation: Moderate

900 m53/100 · mixed

Wind / gust: 20 / 39 mph
Typical / low: 5.7° / 5.5°C · much of the night
In cloud: 69% of 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

Daytime · exposed rockClimbing & scramblingBetaGusts near 35 mph increase the seriousness of exposed ground. 3/100Poor · Very poor View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (3/100). Rain during the useful part of the day is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 35 mph; crosswinds can make exposed ridges substantially more serious. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust33 mphRain2.4 mm

Main factorsgusts around 35 mphwet rock likelymuch of the route may be in cloud

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Tuesday 8 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

Wednesday 9 September 2026Medium confidence

Overall hill weather52/100Mixed

Wind15 mph NW Gusts21 mph Feels1°C Rain1.3 mm Cloud-free summit40% Cloud base through day600–2,000 m Freezing levelAbove summit Daylight06:38–19:47 · 13.1 h

Forecast confidence: Rain could reach the main walking period or hold off until later; forecast models disagree on the timing.

Cloud-free timing: Around 20% early, improving to around 60% later.

A mixed day on Pen yr Ole Wen: summit wind broadly 5-20 mph, with gusts 15-25 mph early in the morning (fresh and blowy). Cloud base around 600–900 m in the morning, lifting to 800–1100 m around midday and 1700–2000 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from late afternoon into the evening. Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud. A generally bright day is indicated, with about 11 hours of sunshine. Some rain is likely, with up to around 2 mm indicated; timing and local totals remain uncertain. Cold on top: air temperature broadly 4 to 8°C, feeling around 0 to 4°C in the wind - wrap up. Cloud base is the least certain part of this - it could sit a couple of hundred metres either way, especially where it is close to summit level.

At this mountain

Sunshine and sky

Generally bright. A generally bright day is indicated.

Modelled sunshine10.9 h84% of daylight

Early2 h sunshine

Midday4 h sunshine

Later3.1 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Poor

34/100

Afternoon & evening · 13:00–22:00Mixed

69/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaConditions look very good, but forecast uncertainty caps the grade at 82/100. 82/100Good · 600 m View detailsHide details

Night beginning Wednesday 9 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (82/100). A lower pitch near 300 m looks more comfortable; conditions are less suitable by 900 m. Wind should be light enough for most well-chosen pitches. Peak gusts increase from about 15 mph at 300 m to 20 mph at 900 m. Little overnight rain is expected. From around 900 m upward, pitches may spend part of the night in cloud, bringing persistent damp and poor visibility. The coldest temperature falls from about 8.3°C at 300 m to 5.7°C at 900 m. Forecast models are not closely enough agreed for an exceptional grade. The grade is capped at 82/100.

Overnight rain0.0 mm Open ground · 600 m6 mph · gusts 15 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m82/100 · promising

Wind / gust: 5 / 13 mph
Typical / low: 8.7° / 8.3°C · much of the night
In cloud: Unlikely
Condensation: Low

600 m82/100 · promising

Wind / gust: 6 / 15 mph
Typical / low: 8.7° / 8.3°C · much of the night
In cloud: Unlikely
Condensation: Low

900 m54/100 · mixed

Wind / gust: 7 / 18 mph
Typical / low: 6.1° / 5.7°C · much of the night
In cloud: 50% of 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

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely during the useful part of the day. 26/100Poor · Poor View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (26/100). Rain during the useful part of the day is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust19 mphRain0.9 mm

Main factorswet rock likelymuch of the route may be in cloud

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Wednesday 9 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

Thursday 10 September 2026Medium confidence

Overall hill weather52/100Mixed

Wind12 mph W Gusts17 mph Feels3°C Rain0.0 mm Cloud-free summit50% Cloud base through day800–1,800 m Freezing levelAbove summit Daylight06:40–19:44 · 13.1 h

Forecast confidence: Rain timing may shift by several hours, which could change how much of the main walking period stays dry.

Cloud-free timing: Around 30% early, improving to around 50% later.

A mixed day on Pen yr Ole Wen: summit wind broadly 5-15 mph, with gusts 10-20 mph during the evening (a moderate breeze). Cloud base around 800–1100 m in the morning, lifting to 1000–1300 m around midday and 1500–1800 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from the morning into the afternoon. Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud. Broken cloud should allow about 7 hours of sunshine in brighter spells. Little or no rain expected. Cloud base is the least certain part of this - it could sit a couple of hundred metres either way, especially where it is close to summit level.

At this mountain

Sunshine and sky

Useful bright spells. Some sunshine is indicated between duller spells.

Modelled sunshine6.7 h52% of daylight

Early1 h sunshine

Midday2.7 h sunshine

Later1.7 h sunshine

These are direct modelled sunshine hours during daylight, not the probability of sunshine. Cloud cover and summit cloud are assessed separately in the forecast above. Local hill cloud can still make an individual summit brighter or duller than the surrounding model grid.

Morning · 07:00–13:00Poor

49/100

Afternoon & evening · 13:00–22:00Mixed

55/100

Separate hill-weather grades help compare an early start with later conditions; the main daytime forecast above still covers the core walking day.

Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 35 mph make meaningful shelter important. 39/100Poor · 600 m View detailsHide details

Night beginning Thursday 10 September 2026

Full overnight outlook

Open-hillside camping looks poor overall around 600 m (39/100). Open-ground gusts may reach about 35 mph; seek meaningful shelter. Peak gusts increase from about 25 mph at 300 m to 35 mph at 900 m. Wind may shift from westerly to northerly; shelter that works at dusk may be less effective later. A wet night is likely, with roughly 15.1 mm; the wettest inconvenience is most likely around pack-up. From around 900 m upward, pitches may spend part of the night in cloud, with high condensation risk, persistent damp and poor visibility; ventilation will matter. The coldest temperature falls from about 9.8°C at 300 m to 7.9°C at 900 m.

Overnight rain15 mm Open ground · 600 m15 mph · gusts 31 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Elevation reference (open ground)

300 m39/100 · poor

Wind / gust: 13 / 26 mph
Typical / low: 10.6° / 9.8°C · a brief spell
In cloud: Unlikely
Condensation: High

600 m39/100 · poor

Wind / gust: 15 / 31 mph
Typical / low: 10.6° / 9.8°C · a brief spell
In cloud: Unlikely
Condensation: High

900 m39/100 · poor

Wind / gust: 18 / 37 mph
Typical / low: 9.3° / 7.9°C · much of the night
In cloud: 50% of 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

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying after recent rain. 52/100Mixed · Mixed View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (52/100). Some rock may still be damp or drying; polished slabs and vegetated sections could be notably worse. The mapped summit rock is Mudstone and siltstone (Cwm Eigiau Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Representative samples along available mapped routes also include Felsic tuff, Siltstone and 2 other mapped types, so rock character and wet-weather behaviour may change across the mountain.

Rock surfaceDamp or dryingPeak gust16 mphRainPossible · 65%

Main concerndamp or incompletely dried rock possible

Mapped rock across the summit and available routes Mudstone and siltstone Cwm Eigiau Formation

Origin: Sedimentary
Rock family: Slate or mudstone
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. 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.

Mapped variation

5 rock types appear across the available route samples

The summit type remains the forecast's cautious rock-response reference. Other mapped types show where conditions may behave differently elsewhere on the mountain.

Summit mapping Mudstone and siltstone Cwm Eigiau Formation 767–860 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Felsic tuff Capel Curig Volcanic Formation 306–680 m samples Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Siltstone Capel Curig Volcanic Formation 392–580 m samples Seen on Peak Carneddau Ogwen

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

BGS record

Route sample Rhyolite Unnamed Igneous Intrusion, Ordovician Around 488 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.

BGS record

Route sample Sandstone Llewelyn Volcanic Group Around 955 m Seen on Peak Carneddau Ogwen

Often grippy when dry, but wet sandstone can lose strength and may be damaged by climbing. Avoid it while saturated and allow shaded walls, pockets and seepage lines time to dry.

BGS record

See sampled routes

Peak Carneddau Ogwen306–955 m samplesFelsic tuff · Mudstone and siltstone · Siltstone · Rhyolite · Sandstone

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

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 Pen yr Ole Wen on Thursday 10 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

Pen yr Ole Wen weather forecast.

Today on Pen yr Ole Wen.

Seven-day Pen yr Ole Wen forecast.

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

Full overnight outlook

Elevation reference (open ground)

Full climbing & scrambling outlook

5 rock types appear across the available route samples

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