The day on the hill
Strong gusts and frequent summit cloud on A' Ghlas-bheinn: summit wind broadly 20-40 mph, with gusts 40-50 mph at times (strong winds). Visibility may drop briefly in showers.
Wind & exposure
Much calmer lower down - generally 10-20 mph in the valley, rising towards the tops. Gusts may knock you off balance on exposed ground, even between spells of lighter wind.
Cloud & views
Cloud base around 500–800 m in the morning, lifting to 800–1100 m around midday. 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
The ground is likely to be saturated after recent rain. Expect boggy paths and rapid runoff if more rain arrives.
Some rain may fall as showers. The forecast total is up to around 2 mm, but local amounts will vary.
Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around -6 to -2°C in the wind. Forecast models differ on summit wind strength: around 32-36 mph at walker height, with gusts 45-50 mph.
Forecast confidence
Cloud height remains uncertain, especially where it is close to summit level. Keep windproof and warm layers readily available.
Cloud-height uncertainty could put the summit in or out of cloud, even where forecasts agree on the wider cloud cover.
Cloud-free timing: Around 10% early, improving to around 45% later.
Sunshine context Model-grid estimate, not summit sunshine
The surrounding model grid indicates 2.3 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
- 0 h
- Midday
- 2.2 h
- Later
- 0 h
Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.
Overnight · 17:00–08:00Wild campingBetaGusts near 40 mph make meaningful shelter important. 59/100Mixed · 600 m View detailsHide details
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 25 mph at 300 m to 40 mph at 900 m. Wind direction may change substantially during the night. Shelter that works at dusk may be less effective later. Around 2.1 mm is forecast, 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 900 m. Ventilation will matter. The coldest temperature falls from about 6.9°C at 300 m to 4.9°C at 900 m.
Moon overnight
Waxing gibbous moon
- Illuminated disc
- 70%
- Moonrise
- 17:57 BST
- Moonset
- 23:45 BST
Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.
Overnight window: 20 Sep, 17:00 BST to 21 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.
Elevation reference (open ground)
- Wind / gust
- 14 mph / 27 mph
- Typical / low
- 7.5°C / 6.9°C · much of the night
- In cloud
- 0% of modelled night
- Condensation
- Moderate
- Wind / gust
- 16 mph / 33 mph
- Typical / low
- 7.5°C / 6.9°C · much of the night
- In cloud
- 0% of modelled night
- Condensation
- Moderate
- Wind / gust
- 19 mph / 39 mph
- Typical / low
- 5.6°C / 4.9°C · a brief spell
- In cloud
- 73% 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.
The ground is likely to be very wet after recent rain. Expect boggy approaches and choose a durable pitch carefully.
Open-hillside reference. A sheltered pitch may be calmer; cols and ridges may be much windier. Tent design and the exact pitch still matter. Read about sleeping-bag comfort ratings, pitching in strong winds or using the wild-camping forecast.
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Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 45 mph may affect balance on exposed rock. Poor0/100 View detailsHide details
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 Psammite and semipelite (Morar Group). Dry quartz-rich bands can be grippy, while mica-rich or foliated sections, lichen and vegetation may become slippery when wet. Representative samples along available mapped routes also include Felsite, Porphyritic microdiorite and 1 other mapped type, 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.
Dry quartz-rich bands can be grippy, while mica-rich or foliated sections, lichen and vegetation may become slippery when wet. 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.
A' Ghlas-bheinn
psammite, pelite or semipelite, volcanic rock, granite, gneiss or gabbro
Geological detail and BGS records
4 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.
Dry quartz-rich bands can be grippy, while mica-rich or foliated sections, lichen and vegetation may become slippery when wet.
BGS recordOften 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 recordDry quartz-rich bands can be grippy, while mica-rich or foliated sections, lichen and vegetation may become slippery when wet.
BGS recordGeneric 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.
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Overnight · Aurora, stars & meteorsAfter darkBetaCloud is likely to obscure much of the sky. View forecastClose forecast
After dark: aurora and stargazing
Night beginning 2026-09-20. All times are UK local time.
Stargazing
Poor sky conditions during the best available spell: 21 Sep, 02:00 BST to 03:00 BST.
Cloud is likely to obscure much of the sky.
Moon-free dark sky: 20 Sep, 23:35 BST to 21 Sep, 04:50 BST.
Sky conditions through the night
| Time | Viewing conditions |
|---|---|
| 20 Sep, 21:40 BST to 22:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 20 Sep, 22:00 BST to 23:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 20 Sep, 23:00 BST to 21 Sep, 00:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 21 Sep, 00:00 BST to 01:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 21 Sep, 01:00 BST to 02:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 21 Sep, 02:00 BST to 03:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 21 Sep, 03:00 BST to 04:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. Rain may interrupt viewing. |
| 21 Sep, 04:00 BST to 04:50 BST | Poor sky conditions Cloud is likely to obscure much of the sky. Rain may interrupt viewing. |
Moon, darkness and meteor showers
Gibbous moon, about 69% illuminated.
Moonrise around 20 Sep, 18:05 BST.
Moonset around 20 Sep, 23:35 BST.
Full darkness: 20 Sep, 21:40 BST to 21 Sep, 04:50 BST.
Moon times assume an open horizon. Hills can hide the Moon sooner. Moon-free does not mean cloud-free.
Southern Taurids are active on this night. Activity may be much lower away from the peak.
- Draconids: peak around 9 October 2026.
- Southern Taurids: peak around 10 October 2026.
- Orionids: peak around 21 October 2026.
- Northern Taurids: peak around 12 November 2026.
- Leonids: peak around 18 November 2026.
- Geminids: peak around 14 December 2026.
- Ursids: peak around 22 December 2026.
Dates from the Royal Observatory Greenwich. Activity dates do not guarantee visible meteors. Look across a broad, dark sky, not only north.
Darkness of the surroundings
Estimated darkness rank 93 of 980 assessed peaks (1 is darkest), based on surrounding artificial light in 2021. This is not a measurement of tonight’s sky.
2021 artificial-light baseline, not measured sky brightness or a Bortle class. Changes to lighting, blue-rich LEDs, terrain screening, atmospheric scattering and cloud-reflected light are not resolved. Similar ranks are not meaningfully distinct. Darkness is not a recommendation to climb a summit at night.
VIIRS nighttime lights: Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines. Reprocessed by OpenGeoHub/OpenLandMap. Cropped and ranked by Mountain Weather.
Sky-weather grades exclude light pollution, terrain and thin haze. They are not mountain safety ratings. Check the mountain and camping forecast separately. Accessible lower viewpoints may be a better choice than summits.
Recommended kit for this dayWeather-aware packing prompts, plus your core hillwalking kitView kit
For a day hillwalk, not a complete route-specific checklist. Carry navigation and backup you can use, warm and waterproof layers, suitable footwear, food and water, a headtorch, emergency shelter, first aid and a way to call for help. Snow, ice, technical terrain and overnight trips need additional equipment and skills.
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