Tryfan Weather Forecast – 918m, Eryri (Snowdonia)

Monday 21 September 2026Confidence: Medium

Overall hill weather66/100Mixed

Wind5-20 mph westerly Gusts15-25 mph Feels like8 to 12°C PrecipitationLittle or none Cloud-free summit estimate25% Cloud base through day600-900 m Freezing levelAbove summit Last observed cloud baseAbove about 850 m 21 September 2026, 19:00 BSTProvisional webcam estimate, above sea level. With thanks to ULGMC. View webcam & overlay DaylightSunrise 06:59 · Sunset 19:17 · 12.3 hours daylight

The day on the hill

Frequent summit cloud on Tryfan: summit wind broadly 5-20 mph, with gusts 15-25 mph at times (a moderate breeze).

Cloud & views

Cloud base mostly around 600–900 m through daylight. Summit cloud is likely, but brief clear spells remain possible if the cloud sits higher than expected.

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

Any sunshine may be confined to lower ground or breaks away from the summit.

Rain & temperature

The ground is likely to be wet after recent rain. 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.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 5.9 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.

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

Early: 0 h
Midday: 2 h
Later: 2.9 h

Webcam cloud observations Experimental

21 September 2026 · 19:00 BST

Cloud base above about 850 m in the camera view (provisional).

Earlier observations that day

18:45 BSTCloud base above about 850 m in the camera view (provisional).
18:30 BSTCloud base above about 850 m in the camera view (provisional).
18:15 BSTCloud base above about 850 m in the camera view (provisional).
18:00 BSTCloud base above about 850 m in the camera view (provisional).
17:45 BSTCloud base above about 850 m in the camera view (provisional).
17:15 BSTCloud base above about 850 m in the camera view (provisional).

Camera-based estimates for the slopes in view, not the whole mountain. Heights are approximate and have not been independently checked. These observations do not replace the forecast.

View webcam photo and cloud overlay

Camera feed timestamp: 21 September 2026, 19:00 BST. These rolling images may have refreshed since the cloud-base reading above. Still images, not live video.

Tryfan webcam photograph — Original webcam photograph. Open full-size photo

Tryfan webcam with cloud analysis overlay — Cloud analysis overlay added by Mountain Weather. Open full-size overlay

With thanks to University of London Graduate Mountaineering Club (ULGMC), Caseg Fraith Hut. Used with permission. Image analysis and overlays by Mountain Weather.

Visit the provider’s current webcam ↗

Explore cloud-base observations, the camera view and daily downloads

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

Morning · 08:00–12:00 Mixed Summit winds around 5-15 mph. Gusts around 15-25 mph are possible on exposed ground.

66/100

Afternoon · 12:00–17:00 Mixed Summit winds around 5-15 mph. Gusts around 15-25 mph are possible on exposed ground.

66/100

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, 600 and 900 m. 64/100Mixed · 600 m View detailsHide details

Night beginning Monday 21 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). Light winds are expected on open ground, though local shelter and exposure still matter. Little overnight rain is forecast. Pitches near 900 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, 600 and 900 m. Ventilation will matter.

Overnight rain0.0 mm Open ground · 600 m4 mph · gusts 13 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 10°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc: 78%
Moonrise: 17:40 BST
Moonset: 01:30 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 m64/100 · reasonable

Wind / gust: 4 mph / 11 mph
Typical / low: 14.3°C / 12.7°C
In cloud: 0% of modelled night
Condensation: High

600 m64/100 · reasonable

Wind / gust: 4 mph / 13 mph
Typical / low: 14.3°C / 12.7°C
In cloud: 0% of modelled night
Condensation: High

900 m54/100 · mixed

Wind / gust: 5 mph / 15 mph
Typical / low: 13.1°C / 11.6°C
In cloud: 100% 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

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Mixed56/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (56/100). Recent rain may leave seepage and damp rock, especially on shaded sections. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 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 surfaceDry overhead; seepage uncertainPeak gust18 mphRain0.0 mm

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

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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

Tuesday 22 September 2026Confidence: Medium

Overall hill weather65/100Mixed

Wind0-15 mph southwesterly Gusts10-20 mph Feels like8 to 12°C PrecipitationUp to around 2 mm Cloud-free summit estimate20% Cloud base through day600-900 m Freezing levelAbove summit DaylightSunrise 07:01 · Sunset 19:15 · 12.2 hours daylight

The day on the hill

Frequent summit cloud on Tryfan: summit wind broadly 0-15 mph, with gusts 10-20 mph at times (light winds).

Cloud & views

Cloud base mostly around 600–900 m through daylight. Summit cloud is likely, but brief clear spells remain possible if the cloud sits higher than expected.

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

Any sunshine may be confined to lower ground or breaks away from the summit.

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.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 4.5 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

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

Early: 1.6 h
Midday: Less than 1 hour
Later: 1.4 h

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

Morning · 08:00–12:00 Mixed Summit winds around 0-10 mph. Gusts around 5-15 mph are possible on exposed ground.

66/100

Afternoon · 12:00–17:00 Mixed Summit winds around 0-10 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is forecast during this period.

64/100

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

Overnight · 17:00–08:00Wild campingBetaGusts near 40 mph make meaningful shelter important. 59/100Mixed · 600 m View detailsHide details

Night beginning Tuesday 22 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (59/100). 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 range from about 30 mph at 300 m to 40 mph at 900 m. Roughly 5 mm is forecast overnight, including rain around pack-up. Pitches near 900 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, 600 and 900 m. Ventilation will matter. The coldest temperature falls from about 11.1°C at 300 m to 9.4°C at 900 m.

Overnight rain5.0 mm Open ground · 600 m13 mph · gusts 34 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc: 86%
Moonrise: 17:57 BST
Moonset: 02:49 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 m59/100 · mixed

Wind / gust: 11 mph / 28 mph
Typical / low: 12.6°C / 11.1°C
In cloud: 0% of modelled night
Condensation: High

600 m59/100 · mixed

Wind / gust: 13 mph / 34 mph
Typical / low: 12.6°C / 11.1°C
In cloud: 0% of modelled night
Condensation: High

900 m39/100 · poor

Wind / gust: 16 mph / 40 mph
Typical / low: 11.0°C / 9.4°C · a brief spell
In cloud: 60% 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 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

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor42/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (42/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 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 gust15 mphRain0.2 mm

Main factorswet rock likelymuch of the route may be in cloud

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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.

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

Wednesday 23 September 2026Confidence: Medium

Overall hill weather30/100Poor

Wind15-35 mph northwesterly Gusts35-45 mph Feels like-2 to 2°C PrecipitationAround 10-20 mm Cloud-free summit estimate40% Cloud base through day600-1,100 m Freezing levelAbove summit DaylightSunrise 07:02 · Sunset 19:13 · 12.2 hours daylight

The day on the hill

Frequent summit cloud on Tryfan: summit wind broadly 15-35 mph, with gusts 35-45 mph at times (strong winds). Hill cloud may make navigation difficult, with very poor visibility in wetter spells.

Things to watch

High spate risk from the morning into the afternoon, with forecast rain and subsequent runoff. Timings are approximate, not a guarantee of safe crossings afterwards. Burns and unbridged crossings may become difficult or impassable. Turn back if a crossing looks unsafe.

Cloud & views

Cloud base around 600–900 m through the morning, lifting to 800–1100 m by late afternoon. Cloud is likely to cover the top for much of the day, though a brief clearance is possible during 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 northwestern slopes and lift somewhat on the southeastern side, but local terrain can differ. Any sunshine may be confined to lower ground or breaks away from the summit.

Rain & temperature

Rain is likely to include a heavy spell, with around 10-20 mm expected over the assessed day. Cold on exposed tops: air temperature broadly 4 to 8°C, feeling around -2 to 2°C in the wind.

Forecast models differ on summit wind strength: around 21-35 mph at walker height, with gusts 29-49 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. A windproof layer will help, with an extra warm layer for stops.

If clothing gets wet, you can cool more quickly. Keep a dry warm layer protected.

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: Around 15% early, improving to around 75% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 5.4 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

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

Early: 0 h
Midday: 1.6 h
Later: 3 h

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

Morning · 08:00–12:00 Poor Summit winds around 25-35 mph early in the morning, easing to 15-25 mph later. Gusts around 35-45 mph are possible on exposed ground. Buffeting may affect balance on exposed ground, particularly near ridges and edges. Rain is forecast during this period. Rain is forecast during the morning, but models differ considerably on the amount. Rain is possible during the main walking period, but its timing may shift by several hours.

12/100

Afternoon · 12:00–17:00 Poor Rain eases compared with the morning. Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Rain is possible during the main walking period, but its timing may shift by several hours.

48/100

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 92/100. 92/100Excellent · 600 m View detailsHide details

Night beginning Wednesday 23 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (92/100). It may be breezy on open ground, with gusts near 25 mph. Peak gusts range from about 15 mph at 300 m to 25 mph at 900 m. Little overnight rain is forecast. The coldest temperature falls from about 8.4°C at 300 m to 5.5°C at 900 m. The forecast does not have sufficiently broad dry and light-wind support for an exceptional grade. The grade is capped at 92/100.

Overnight rain0.0 mm Open ground · 600 m8 mph · gusts 20 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc: 92%
Moonrise: 18:10 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 m92/100 · very good

Wind / gust: 7 mph / 17 mph
Typical / low: 8.4°C / 8.4°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

600 m92/100 · very good

Wind / gust: 8 mph / 20 mph
Typical / low: 8.4°C / 8.4°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

900 m84/100 · promising

Wind / gust: 9 mph / 24 mph
Typical / low: 6.0°C / 5.5°C · much of the night
In cloud: 7% 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

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 40 mph may affect balance on exposed rock. Poor0/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (0/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 40 mph. Crosswinds can make exposed ridges substantially more serious. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust40 mphRain12.9 mm

Main factorsgusts around 40 mphwet rock likelymuch of the route may be in cloud

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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

Thursday 24 September 2026Confidence: Medium

Overall hill weather76/100Good

Wind10-30 mph southwesterly Gusts30-40 mph Feels like2 to 6°C PrecipitationLittle or none Cloud-free summit estimate95% Freezing levelAbove summit DaylightSunrise 07:04 · Sunset 19:10 · 12.1 hours daylight

The day on the hill

On Tryfan: summit wind broadly 10-30 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 1600–1900 m in the morning, then around 2100–2400 m around midday and 1600–1900 m by late afternoon. The summit is likely to stay mostly clear.

Rain & temperature

The ground is likely to be wet after recent rain. Little or no rain is forecast.

Forecast models differ on summit wind strength: around 19-32 mph at walker height, with gusts 27-45 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.

Summit wind could be roughly 19-32 mph, which changes how difficult exposed walking may feel.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 6.8 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: 1 h
Midday: 3.5 h
Later: 1 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 Mixed Winds strengthen compared with the morning. Summit winds around 15-25 mph in the early afternoon, strengthening to 20-30 mph later. Gusts around 30-40 mph are possible on exposed ground. Buffeting may affect balance on exposed ground, particularly near ridges and edges.

61/100

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

Overnight · 17:00–08:00Wild campingBetaGusts near 35 mph make meaningful shelter important. 54/100Mixed · 600 m View detailsHide details

Night beginning Thursday 24 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 35 mph. Seek meaningful shelter. Peak gusts range from about 25 mph at 300 m to 35 mph at 900 m. Little overnight rain is forecast. Pitches near 600 and 900 m may spend part of the night in cloud, bringing damp conditions and poor visibility while cloud is present. The coldest temperature falls from about 10.4°C at 300 m to 8.4°C at 900 m.

Overnight rain0.0 mm Open ground · 600 m17 mph · gusts 29 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc: 97%
Moonrise: 18:21 BST
Moonset: 05:27 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: 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 m82/100 · promising

Wind / gust: 14 mph / 24 mph
Typical / low: 10.5°C / 10.4°C
In cloud: 0% of modelled night
Condensation: Moderate

600 m54/100 · mixed

Wind / gust: 17 mph / 29 mph
Typical / low: 10.5°C / 10.4°C
In cloud: 60% of modelled night
Condensation: Moderate

900 m54/100 · mixed

Wind / gust: 19 mph / 34 mph
Typical / low: 9.1°C / 8.4°C · much of the night
In cloud: 80% 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

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Gusts near 35 mph may affect balance on exposed rock. Mixed59/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (59/100). Recent rain may leave seepage and damp rock, especially on shaded sections. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 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 gust36 mphRain0.0 mm

Main factorsgusts around 35 mphdamp or incompletely dried rock possible

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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

Friday 25 September 2026Confidence: Medium

Overall hill weather40/100Poor

Wind10-25 mph westerly Gusts25-35 mph Feels like0 to 4°C PrecipitationAround 10-20 mm Cloud-free summit estimate15% Cloud base through day500-800 m Freezing levelAbove summit DaylightSunrise 07:06 · Sunset 19:08 · 12.0 hours daylight

The day on the hill

A wet day with extensive summit cloud on Tryfan: summit wind broadly 10-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Cloud & views

Cloud base mostly around 500–800 m through daylight. Summit cloud is likely, but brief clear spells remain possible if the cloud sits higher than expected.

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

Cloud may hang lower on western slopes and lift somewhat on the eastern side, but local terrain can differ. Any sunshine may be confined to lower ground or breaks away from the summit.

Rain & temperature

Rain and drizzle are forecast for much of the day. The forecast total is around 10-20 mm, but local amounts will vary.

Cold on exposed tops: air temperature broadly 4 to 8°C, feeling around 0 to 4°C in the wind. Forecast models differ on summit wind strength: around 14-29 mph at walker height, with gusts 20-40 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. A windproof layer will help, with an extra warm layer for stops.

If clothing gets wet, you can cool more quickly. Keep a dry warm layer protected.

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

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 6.3 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

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

Early: Less than 1 hour
Midday: 4 h
Later: Less than 1 hour

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. Rain is possible during the morning, but forecast models disagree on whether it will fall.

37/100

Afternoon · 12:00–17:00 Poor Winds ease compared with the morning. More rain is expected. Summit winds around 5-20 mph. Gusts around 20-30 mph are possible on exposed ground. Rain is forecast during this period. Some forecast models bring rain during the afternoon, while others keep it mostly dry.

44/100

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

Overnight · 17:00–08:00Wild campingBetaAbout 1.6 mm is forecast, with rain possible around pitching time. 80/100Good · 600 m View detailsHide details

Night beginning Friday 25 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (80/100). It may be breezy on open ground, with gusts near 25 mph. Peak gusts range from about 15 mph at 300 m to 25 mph at 900 m. Around 1.6 mm is forecast, including rain around pitching time.

Overnight rain1.6 mm Open ground · 600 m10 mph · gusts 19 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 4°C or lower

Moon overnight

Near-full moon

Illuminated disc: 99%
Moonrise: 18:31 BST
Moonset: 06:48 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: 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 m80/100 · promising

Wind / gust: 8 mph / 16 mph
Typical / low: 9.2°C / 7.6°C · much of the night
In cloud: 0% of modelled night
Condensation: Low

600 m80/100 · promising

Wind / gust: 10 mph / 19 mph
Typical / low: 9.2°C / 7.6°C · much of the night
In cloud: 13% of modelled night
Condensation: Low

900 m80/100 · promising

Wind / gust: 12 mph / 23 mph
Typical / low: 7.4°C / 6.2°C · much of the night
In cloud: 20% 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

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 30 mph may affect balance on exposed rock. Poor5/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (5/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 30 mph. Crosswinds can make exposed ridges substantially more serious. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust30 mphRain13.2 mm

Main factorsgusts around 30 mphwet rock likelymuch of the route may be in cloud

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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

Saturday 26 September 2026Confidence: Medium

Overall hill weather86/100Excellent

Possible inversionLow confidence · Afternoon

Wind5-15 mph southwesterly Gusts15-25 mph Feels like4 to 8°C PrecipitationLittle or none Cloud-free summit estimate95% Cloud base through day1,100-1,800 m Freezing levelAbove summit DaylightSunrise 07:07 · Sunset 19:05 · 12.0 hours daylight

The day on the hill

Little rain and limited summit cloud on Tryfan: summit wind broadly 5-15 mph, with gusts 15-25 mph at times (light winds).

Cloud & views

Cloud base around 1100–1400 m in the morning, lifting to 1500–1800 m around midday. 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.

Rain & temperature

The ground is likely to be wet after recent rain. Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Rain could reach the main walking period or hold off until later. Forecast models disagree on the timing.

Cloud-free timing: Around 80% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 1.1 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.

Early: 0 h
Midday: Less than 1 hour
Later: Less than 1 hour

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 10-20 mph are possible on exposed ground.

89/100

Afternoon · 12:00–17:00 Good Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later. Rain is possible during the afternoon, but forecast models disagree on whether it will fall.

83/100

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 82/100. 82/100Good · 600 m View detailsHide details

Night beginning Saturday 26 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (82/100). It may be breezy on open ground, with gusts near 20 mph. Peak gusts range from about 15 mph at 300 m to 20 mph at 900 m. Little overnight rain is forecast. The coldest temperature falls from about 10.2°C at 300 m to 8.1°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 m8 mph · gusts 17 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Near-full moon

Illuminated disc: 100%
Moonrise: 18:41 BST
Moonset: Outside this window

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

Overnight window: 26 Sep, 17:00 BST to 27 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m82/100 · promising

Wind / gust: 7 mph / 15 mph
Typical / low: 10.2°C / 10.2°C
In cloud: 0% of modelled night
Condensation: Low

600 m82/100 · promising

Wind / gust: 8 mph / 17 mph
Typical / low: 10.1°C / 10.0°C · a brief spell
In cloud: 0% of modelled night
Condensation: Low

900 m82/100 · promising

Wind / gust: 10 mph / 20 mph
Typical / low: 8.6°C / 8.1°C · much of the night
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 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

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Mixed61/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (61/100). Recent rain may leave seepage and damp rock, especially on shaded sections. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 other mapped types, so rock character and wet-weather behaviour may change across the mountain.

Rock surfaceDry overhead; seepage uncertainPeak gust18 mphRainPossible · 52%

Main concerndamp or incompletely dried rock possible

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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

Sunday 27 September 2026Confidence: Unavailable

Overall hill weather74/100Good

Wind10-25 mph southerly Gusts20-30 mph Feels like2 to 6°C PrecipitationLittle or none Cloud-free summit estimate50% Cloud base through day500-1,700 m Freezing levelAbove summit DaylightSunrise 07:09 · Sunset 19:03 · 11.9 hours daylight

The day on the hill

On Tryfan: summit wind broadly 10-25 mph, with gusts 20-30 mph at times (a fresh breeze). Patchy mist is possible in sheltered valleys early on.

Cloud & views

Cloud base around 1300–1600 m in the morning, then around 1400–1700 m around midday and 500–800 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from early morning into around midday.

Cloud may hang lower on southern slopes and lift somewhat on the northern 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.

Rain & temperature

Little or no rain is forecast. Forecast models differ on summit wind strength.

Treat the wind figures as a guide. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops.

Forecast confidence

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

Cloud-free timing: Around 95% early, falling to around 10% 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

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

90/100

Afternoon · 12:00–17:00 Mixed Summit winds around 15-25 mph. Gusts around 20-30 mph are possible on exposed ground. Summit cloud becomes more persistent later.

57/100

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

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Mixed64/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (64/100). Some rock may still be damp or drying, especially on polished slabs and vegetated sections. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 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 surfaceDamp or dryingPeak gust26 mphRain0.0 mm

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

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan 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

Monday 28 September 2026Confidence: Unavailable

Overall hill weather78/100Good

Wind15-35 mph southwesterly Gusts35-45 mph Feels like0 to 4°C PrecipitationUp to around 2 mm Cloud-free summit estimate95% Freezing levelAbove summit DaylightSunrise 07:11 · Sunset 19:00 · 11.8 hours daylight

The day on the hill

On Tryfan: summit wind broadly 15-35 mph, with gusts 35-45 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 1200–1500 m in the morning, lifting to 1500–1800 m around midday and 1400–1700 m by late afternoon. The summit is likely to stay mostly clear.

Drizzle is forecast for much of the day. The forecast total is up to around 2 mm, but local amounts will vary.

Exposed tops may feel chilly in the wind. A windproof layer will help, with an extra warm layer for stops.

If clothing gets wet, you can cool more quickly. Keep a dry warm layer protected.

Buffeting may affect balance on exposed ground, particularly near ridges and edges.

Forecast confidence

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

Cloud-free timing: Around 80% early, improving to around 95% 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

Morning · 08:00–12:00 Good Summit winds around 15-25 mph. Gusts around 20-30 mph are possible on exposed ground. Rain is forecast during this period.

83/100

Afternoon · 12:00–17:00 Good Summit winds around 15-25 mph. Gusts around 30-40 mph are possible on exposed ground. Rain is forecast during this period.

74/100

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

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 40 mph may affect balance on exposed rock. Poor40/100 View detailsHide details

Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look mixed (40/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Microgabbro (Unnamed Igneous Intrusion, Ordovician). Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. Representative samples along available mapped routes also include Siltstone, Felsic lava and felsic tuff and 4 other mapped types, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 40 mph. Crosswinds can make exposed ridges substantially more serious.

Rock surfaceWet rock likelyPeak gust38 mphRain1.1 mm

Main factorsgusts around 40 mphwet rock likely

Mapped rock across the summit and available routes Microgabbro Unnamed Igneous Intrusion, Ordovician

Origin: Igneous
Rock family: Granite, gneiss or gabbro
Mapping: BGS Geology 50K · 1:50,000
Rock-response profile: Moderate confidence

View the summit BGS record

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery. 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.

Glyderau Ogwen

slate or mudstone, volcanic rock, sandstone or gritstone

Geological detail and BGS records

Mapped variation

9 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 Microgabbro Unnamed Igneous Intrusion, Ordovician

Generally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.

BGS record

Route sample Siltstone Llewelyn Volcanic Group 648–900 m samples Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Felsic lava and felsic tuff Braich tu du Volcanic Formation Around 399 m Seen on Peak Glyderau 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 Mudstone and siltstone Cwm Eigiau Formation Around 317 m Seen on Peak Glyderau Ogwen

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

BGS record

Route sample Pyroclastic-rock Bedded Pyroclastic Formation Around 731 m Seen on Peak Glyderau 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 Rhyolite Unnamed Igneous Intrusion, Ordovician Around 980 m Seen on Peak Glyderau 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 486 m Seen on Peak Glyderau 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

Route sample Sandstone Cwm Eigiau Formation Around 569 m Seen on Peak Glyderau 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

Route sample Siltstone Lower Rhyolitic Tuff Formation Around 812 m Seen on Peak Glyderau Ogwen

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

BGS record

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

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 Tryfan on Monday 28 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

Tryfan weather forecast.

Choose your hill day.

The day on the hill

Cloud & views

Rain & temperature

Forecast confidence

Webcam cloud observations Experimental

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

Rock groups along the sampled routes

Glyderau Ogwen

9 rock types appear across the available route samples

After dark: aurora and stargazing

The day on the hill

Cloud & views

Rain & temperature

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

Rock groups along the sampled routes

Glyderau Ogwen

9 rock types appear across the available route samples

After dark: aurora and stargazing

The day on the hill

Things to watch

Cloud & views

Rain & temperature

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

Rock groups along the sampled routes

Glyderau Ogwen

9 rock types appear across the available route samples

After dark: aurora and stargazing

The day on the hill

Wind & exposure

Cloud & views

Rain & temperature

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

Rock groups along the sampled routes

Glyderau Ogwen

9 rock types appear across the available route samples

After dark: aurora and stargazing

The day on the hill

Cloud & views

Rain & temperature

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

Rock groups along the sampled routes

Glyderau Ogwen

9 rock types appear across the available route samples

After dark: aurora and stargazing

The day on the hill

Cloud & views

Rain & temperature

Forecast confidence

Full overnight outlook

Moon overnight

Elevation reference (open ground)

Full climbing & scrambling outlook

Rock groups along the sampled routes

Glyderau Ogwen

9 rock types appear across the available route samples

After dark: aurora and stargazing

The day on the hill

Cloud & views

Rain & temperature