The day on the hill
Little rain and limited summit cloud on Butser Hill: summit wind broadly 5-25 mph, with gusts 25-35 mph at times (a fresh breeze).
Cloud & views
Cloud base around 600–900 m in the morning, lifting to 1200–1500 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
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 9.6 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
- 1.8 h
- Midday
- 3.8 h
- Later
- 2 h
Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.
Overnight · 17:00–08:00Wild campingBetaConditions look exceptional, but forecast uncertainty caps the grade at 97/100. 97/100Excellent · 300 m View detailsHide details
Full overnight outlook
Open-hillside camping looks very good overall around 300 m (97/100). Light winds are expected on open ground, though local shelter and exposure still matter. Little overnight rain is forecast. Forecast models strongly support a good night, but not at the exceptional-certainty threshold. The grade is capped at 97/100.
Moon overnight
Waxing gibbous moon
- Illuminated disc
- 70%
- Moonrise
- Outside this window
- Moonset
- 00:15 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: 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
- 5 mph / 11 mph
- Typical / low
- 10.8°C / 8.9°C · several hours
- In cloud
- 0% 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.
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Daytime · exposed rockClimbing & scramblingBetaPatchy rain could leave exposed holds damp or slippery. Excellent86/100 View detailsHide details
Full climbing & scrambling outlook
Conditions for exposed scrambling look good (86/100). Likely to stay mostly dry, but patchy rain remains possible and could leave exposed rock damp or slippery. The mapped summit rock is Chalk (Seaford Chalk Formation). Usually positive where it is rough and dry, but polished limestone can become very slippery when wet and seepage may linger.
Usually positive where it is rough and dry, but polished limestone can become very slippery when wet and seepage may linger. 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.
Popular Butser Hill
limestone
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.
Usually positive where it is rough and dry, but polished limestone can become very slippery when wet and seepage may linger.
BGS recordUsually positive where it is rough and dry, but polished limestone can become very slippery when wet and seepage may linger.
BGS recordUsually positive where it is rough and dry, but polished limestone can become very slippery when wet and seepage may linger.
BGS recordUsually positive where it is rough and dry, but polished limestone can become very slippery when wet and seepage may linger.
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 darkBetaClearer spells are possible, but other forecasts keep much of the sky obscured by cloud. View forecastClose forecast
After dark: aurora and stargazing
Night beginning 2026-09-20. All times are UK local time.
Stargazing
Very good sky conditions during the best available spell: 21 Sep, 00:00 BST to 01:00 BST.
Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud.
Moon-free dark sky: 21 Sep, 00:10 BST to 04:55 BST.
Sky conditions through the night
| Time | Viewing conditions |
|---|---|
| 20 Sep, 21:00 BST to 22:00 BST | Good sky conditions Mostly clear skies are forecast. |
| 20 Sep, 22:00 BST to 23:00 BST | Good sky conditions Mostly clear skies are forecast. |
| 20 Sep, 23:00 BST to 21 Sep, 00:00 BST | Good sky conditions Cloud breaks may offer some views of the stars. |
| 21 Sep, 00:00 BST to 01:00 BST | Very good sky conditions Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud. Forecast models disagree. |
| 21 Sep, 01:00 BST to 02:00 BST | Good sky conditions Clearer spells are possible, but other forecasts keep much of the sky obscured by cloud. Forecast models disagree. |
| 21 Sep, 02:00 BST to 03:00 BST | Very good sky conditions Cloud breaks may offer some views of the stars. |
| 21 Sep, 03:00 BST to 04:00 BST | Mixed sky conditions Cloud is likely to obscure much of the sky. |
| 21 Sep, 04:00 BST to 04:55 BST | Poor sky conditions Cloud is likely to obscure much of the sky. |
Moon, darkness and meteor showers
Gibbous moon, about 69% illuminated.
Moonset around 21 Sep, 00:10 BST.
Full darkness: 20 Sep, 21:00 BST to 21 Sep, 04:55 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 956 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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