Forecast confidence: Cloud height is close to summit level at times, so small local changes could put the top in or out of cloud.
Burns and unbridged crossings may rise quickly. Assess them at the water and turn back if unsure.
Cloud-free timing: Around 30% early, improving to around 60% later.
A grey, cloudy day on Cadair Idris - Penygadair: summit wind broadly 20-35 mph, with gusts 40-50 mph early in 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. Much calmer lower down - generally 15-25 mph in the valley, rising towards the tops. Cloud base around 800–1100 m in the morning, lifting to 700–1000 m around midday and 1400–1700 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from 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 western slopes; the eastern side should see somewhat higher bases and better breaks. about 3 hours of sunshine is indicated, with variable cloud giving brighter and duller 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.
Sunshine and sky
Brighter and duller spells. Expect alternating brighter and duller spells.
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.
Overnight · 6 p.m.–9 a.m.Wild campingBetaGusts near 40 mph make meaningful shelter important. 84/100Good · 600 m View detailsHide details
Full overnight outlook
Open-hillside camping looks promising overall around 600 m (84/100). 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. Little overnight rain is expected. 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 9.5°C at 300 m to 6.8°C at 900 m.
Elevation reference (open ground)
- Wind / gust
- 16 / 30 mph
- Typical / low
- 10.1° / 9.5°C · several hours
- In cloud
- Unlikely
- Condensation
- Low
- Wind / gust
- 19 / 36 mph
- Typical / low
- 10.1° / 9.5°C · several hours
- In cloud
- Unlikely
- Condensation
- Low
- Wind / gust
- 23 / 42 mph
- Typical / low
- 7.9° / 6.8°C · much of the night
- In cloud
- 75% 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
Full climbing & scrambling outlook
Conditions for exposed scrambling look very poor (0/100). Some rock may still be damp or drying; polished slabs and vegetated sections could be notably worse. The mapped summit rock is Tuff and lava (Pen y gadair Volcanic Formation). Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery. Representative samples along available mapped routes also include Microgranite, Mudstone and 4 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. Cloud may also make route-finding and retreat harder.
Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them 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.
8 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.
Often grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.
BGS recordGenerally grippy when dry and often still positive when damp, but wet slabs, lichen, polish and drainage lines can remain slippery.
BGS recordOften positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.
BGS recordOften grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.
BGS recordOften grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.
BGS recordOften positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.
BGS recordOften grippy when dry, but volcanic rocks vary widely; wet lichen, smooth holds and local seepage can still make them slippery.
BGS recordOften positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.
BGS recordSee sampled routes
Peak Cadair Idris Minffordd105–844 m samplesMudstone · Felsic tuff · Mudstone and siltstone · Tuff and lava · Tuffaceous-mudstone with clasts of pillowed basalt and volcaniclastic rock
Peak Cadair Idris Pony Path162–844 m samplesMicrogranite · Basalt · Mudstone · Tuff and lava · Tuff and lava
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 Cadair Idris - Penygadair 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.
About the research and your privacy · Already been out? Share that experience instead
