The day on the hill
Frequent summit cloud on Beinn a' Chreachain: summit wind broadly 15-30 mph, with gusts 30-40 mph at times (a fresh breeze).
Things to watch
High spate risk during the morning, after earlier rain. 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 in the morning, lifting to 1000–1300 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 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
The ground is likely to be wet after recent rain. Some rain is likely, totalling up to around 2 mm, but its timing and local amounts are uncertain.
Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around -4 to 0°C in the wind. Forecast models differ on summit wind strength: around 22-27 mph at walker height, with gusts 30-38 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 5% early, improving to around 60% later.
Sunshine context Model-grid estimate, not summit sunshine
The surrounding model grid indicates 4.4 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
- 1.4 h
- Midday
- 1.2 h
- Later
- 0.8 h
Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.
Overnight · 17:00–08:00Wild campingBetaA cold night is forecast near 900 m, with the cold lasting much of the night. 83/100Good · 600 m View detailsHide details
Full overnight outlook
Open-hillside camping looks promising overall around 600 m (83/100). A lower pitch near 300 m looks more comfortable. Conditions are less suitable by 900 m. It may be breezy on open ground, with gusts near 25 mph. Peak gusts range from about 20 mph at 300 m to 25 mph at 900 m. Wind direction may change substantially during the night. Shelter that works at dusk may be less effective later. Little overnight rain is forecast. The coldest temperature falls from about 5.9°C at 300 m to 3.9°C at 900 m.
Moon overnight
Waxing gibbous moon
- Illuminated disc
- 92%
- Moonrise
- 18:24 BST
- Moonset
- 04:01 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: 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)
- Wind / gust
- 9 mph / 19 mph
- Typical / low
- 6.4°C / 5.9°C · much of the night
- In cloud
- 0% of modelled night
- Condensation
- Low
- Wind / gust
- 11 mph / 23 mph
- Typical / low
- 6.4°C / 5.9°C · much of the night
- In cloud
- 0% of modelled night
- Condensation
- Low
- Wind / gust
- 12 mph / 27 mph
- Typical / low
- 4.5°C / 3.9°C · much of the night
- In cloud
- 13% 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.
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Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 35 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 Garnet semipelite (Coire Daingean Semipelite Formation). 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 Psammite, Semipelite, psammite and quartzite, so rock character and wet-weather behaviour may change across the mountain. Gusts may reach about 35 mph. Crosswinds can make exposed ridges substantially more serious. Cloud may also make route-finding and retreat harder.
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.
Beinn a' Chreachain and Beinn Achaladair
psammite, pelite or semipelite, quartzite
Geological detail and BGS records
3 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 recordDry quartz-rich bands can be grippy, while mica-rich or foliated sections, lichen and vegetation may become slippery when wet.
BGS recordUsually hard and grippy when dry and often reasonably positive when damp, although wet lichen and smooth slabs can still be slippery.
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 darkBetaAurora activity is possible, but cloud, rain or poor visibility may limit the view View forecastClose forecast
After dark: aurora and stargazing
Night beginning 2026-09-23. All times are UK local time.
Aurora activity is possible, but cloud, rain or poor visibility may limit the view
Space-weather forecasts suggest activity could be strong enough for aurora at this location. Forecast activity peaks near Kp 5.3 on the 0 to 9 scale.
Some forecasts suggest fog or very poor visibility could obscure the view.
Look north-north-west, from the horizon part-way up the sky. A clear, open view that way matters more than height.
A bright Moon is above the horizon around the best forecast hour and may wash out faint aurora detail. A stronger display may still be visible.
Aurora viewing guidance
Cloud is sampled overhead and towards the northern viewing horizon. Narrow cloud bands can still be missed. Forecast models disagree on cloud towards the viewing horizon.
The terrain horizon has not been checked at this exact location. Nearby slopes or a lower campsite can have a very different view.
Some surrounding artificial light lies towards the aurora. Local lights may make a faint, low display harder to pick out.
Most likely a faint glow low in the sky that a phone camera shows better than your eyes. It can look like thin cloud.
Not sure what you are seeing? Take a Night-mode photo facing north: rest the phone on a rock or pack, use the main lens and a timer, and hold still for a 3–10 second exposure. Cameras show aurora colour long before eyes do.
Aurora activity can change quickly. This is experimental guidance, not a guaranteed sighting. Check again before heading out.
Stargazing
Mixed sky conditions during the best available spell: 24 Sep, 02:00 BST to 03:00 BST.
Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.
Moon-free dark sky: 24 Sep, 03:50 BST to 05:00 BST.
Sky conditions through the night
| Time | Viewing conditions |
|---|---|
| 23 Sep, 21:25 BST to 22:00 BST | Mixed sky conditions Cloud breaks may offer some views of the stars. Moonlight washes out fainter stars. |
| 23 Sep, 22:00 BST to 23:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. Moonlight washes out fainter stars. |
| 23 Sep, 23:00 BST to 24 Sep, 00:00 BST | Poor sky conditions Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud. Forecast models disagree. |
| 24 Sep, 00:00 BST to 01:00 BST | Poor sky conditions Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud. Forecast models disagree. |
| 24 Sep, 01:00 BST to 02:00 BST | Mixed sky conditions Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud. Forecast models disagree. |
| 24 Sep, 02:00 BST to 03:00 BST | Mixed sky conditions Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud. Forecast models disagree. |
| 24 Sep, 03:00 BST to 04:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
| 24 Sep, 04:00 BST to 05:00 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
Moon, darkness and meteor showers
Gibbous moon, about 92% illuminated.
Moonrise around 23 Sep, 18:25 BST.
Moonset around 24 Sep, 03:50 BST.
Full darkness: 23 Sep, 21:25 BST to 24 Sep, 05:00 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 373 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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