The day on the hill
A poor day on the tops of Y Garn, with drizzle for much of the day and cloud coming and going on the summit.
Wind
On the summit expect a south-easterly wind of 5–20 mph for most of the day, with gusts of 15–25 mph at the windiest. Lower down on the open hillside the wind will be light, under 10 mph.
Cloud and visibility
Expect the summit to be in cloud for most of the day. The cloud base could be as low as 400–700 m in the late afternoon. In cloud you'll be finding your way without landmarks, so carry navigation you trust and know how to use, with a backup such as a spare battery or a map and compass.
Rain and ground
Drizzle for much of the day. Expect 2–5 mm in total. The timing could shift by a few hours.
Warmth and kit
On the tops it will be around 2 to 6°C, feeling like 0 to 4°C in the wind. The freezing level is above the summits. A windproof and an extra layer for stops will help. Pack waterproofs too, and keep a warm layer dry in your pack.
Daylight
Sunset is around 6:10pm, so allow time to get off the hill before dark, and carry a head torch.
Forecast confidence
Things could still change through the day, so keep an eye on the sky.
Sunshine context Model-grid estimate, not summit sunshine
The surrounding model grid indicates 0 h of sunshine. This is not a forecast of time in sunshine on the summit. Use the cloud and views outlook above for the conditions on this mountain.
- Early
- 0 h
- Midday
- 0 h
- Later
- 0 h
Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.
Overnight · 17:00–08:00Wild campingBetaA reasonable night to camp, with a well-chosen pitch: about 3 mm of rain. 64Mixed · 600 m View detailsHide details
Full overnight outlook
A reasonable night to camp, with a well-chosen pitch. Light winds on open ground, gusting no more than about 25 mph. The wind swings from southerly to southeasterly overnight, so a pitch sheltered at dusk may not be by morning. Expect about 3 mm of rain, with rain while you pitch and still falling when you pack up. Overnight lows of about 4°C at 900 m. A 3-season bag rated to about 4°C comfort, and a warm mat, should do. Allow more if you sleep cold.
Moon overnight
Waxing gibbous moon
- Illuminated disc
- 72%
- Moonrise
- Outside this window
- Moonset
- 01:45 next morning BST
Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.
Overnight window: 20 Oct, 17:00 BST to 21 Oct, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.
Elevation reference (open ground)
- Wind / gust
- 9 mph / 17 mph
- Typical / low
- 8.2°C / 7.6°C · much of the night
- In cloud
- 0% of modelled night
- Condensation
- High
- Wind / gust
- 11 mph / 21 mph
- Typical / low
- 6.8°C / 6.4°C · much of the night
- In cloud
- 20% of modelled night
- Condensation
- High
- Wind / gust
- 13 mph / 24 mph
- Typical / low
- 5.0°C / 4.5°C · much of the night
- In cloud
- 20% of modelled night
- Condensation
- High
Warmth planning: As a broad starting point, consider a 3-season bag with an ISO/EN comfort rating at or below about 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.
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Daytime · exposed rockClimbing & scramblingBetaVery poor conditions for exposed scrambling: wet, slippery rock. Poor0 View detailsHide details
Full climbing & scrambling outlook
Very poor conditions for exposed scrambling. The rock is likely to be wet and slippery through the day. Cloud on the tops may make route-finding and retreat harder. The rock changes around the summit, with mudstone or slate, sandstone and volcanic tuff, so its grip and soundness vary as you go. Mudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds. Sandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away. On the usual routes up you may also cross volcanic tuff, which is rough and grippy when dry and usually still grips reasonably when wet. These are general notes for each rock type, taken from geological maps around the summit, so the rock on your line may differ.
The rock changes around the summit, with mudstone or slate, sandstone and volcanic tuff, so its grip and soundness vary as you go. The rock changes over short distances here, so check it directly before you commit to a move. Lichen, vegetation and seepage also change how it feels underfoot.
Rock groups along the sampled routes
These are mapped rock groups, not separate weather forecasts or a ranking of route safety.
Elidir Fawr Ridge
volcanic rock, slate or mudstone, sandstone or gritstone
Glyderau Devils Kitchen
volcanic rock, slate or mudstone, sandstone or gritstone
Glyderau Ogwen
slate or mudstone, volcanic rock, sandstone or gritstone
Geological detail and BGS records
14 rock types appear in the mapped samples
No single rock family dominates the summit-area samples, so the forecast uses cautious mixed-rock guidance. The summit pin is shown separately and may not represent nearby crags. Route samples add context where available.
Volcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.
BGS recordVolcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.
BGS recordMudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.
BGS recordVolcanic tuff is rock formed from compacted volcanic ash and debris. It is rough and grippy when dry and usually still grips reasonably when wet. It is mostly solid, in slabs and ledges, though weathered patches can be crumbly.
BGS recordMudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.
BGS recordRhyolite is a hard, fine-grained volcanic rock. It grips well when dry and gets slippery on smoother faces when wet. It is hard, but often cracked into sharp, blocky pieces, so some holds are loose.
BGS recordSandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.
BGS recordSandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.
BGS recordMudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.
BGS recordMudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.
BGS recordRhyolite is a hard, fine-grained volcanic rock. It grips well when dry and gets slippery on smoother faces when wet. It is hard, but often cracked into sharp, blocky pieces, so some holds are loose.
BGS recordRhyolite is a hard, fine-grained volcanic rock. It grips well when dry and gets slippery on smoother faces when wet. It is hard, but often cracked into sharp, blocky pieces, so some holds are loose.
BGS recordSandstone is a gritty sedimentary rock. It is rough and grippy when dry and can feel greasy when damp or covered in lichen. It is usually solid in terraced steps, but softer layers crumble and weathered edges can break away.
BGS recordMudstone or slate is a soft, fine-grained rock that splits into thin flakes. It has only fair grip even when dry and is slippery when wet. It is often shattered, breaking into loose flakes, scree and poor holds.
BGS recordGeneric exposed scrambling terrain; BGS summit-area bedrock samples are included where available, but route grade, exact rock, polish, drainage and escape options remain unresolved. Contains British Geological Survey materials © UKRI 2026. How to use the climbing and scrambling forecast.
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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.
Explore the dedicated aurora forecast, meteor shower forecast or dark-sky and astrophotography forecast.
Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit
For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.
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