Mountain Weather

Y Llethr weather forecast.

756 m summit in Eryri (Snowdonia). 8 forecast days covering wind, cloud, rain and temperature, updated 20 September 2026 at 16:08 UTC.

Choose your hill day.

Compare 8 days, then read the outlook for your visit. How we score a hill day.

Select a day to replace the detailed forecast below. 8 forecast days are available here.

Confidence: Medium
Overall hill weather86/100Excellent
Wind10-25 mph westerly Gusts25-35 mph Feels like2 to 6°C PrecipitationLittle or none Cloud-free summit estimate85% Cloud base through day800-1,700 m Freezing levelAbove summit DaylightSunrise 06:57 · Sunset 19:20 · 12.4 hours daylight

The day on the hill

On Y Llethr: summit wind broadly 10-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Cloud & views

Cloud base around 800–1100 m in the morning, then around 1400–1700 m around midday and 1100–1400 m by late afternoon. 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

The ground is likely to be wet after recent rain. Little or no rain is forecast.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. 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 50% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 10.1 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
4 h
Later
2.4 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Good Summit winds around 10-25 mph. Gusts around 25-35 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later.
82/100
Afternoon · 12:00–17:00 Excellent Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground.
90/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaConditions look exceptional, but forecast uncertainty caps the grade at 97/100. 97/100Excellent · 600 m View detailsHide details
Night beginning Sunday 20 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 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.

Overnight rain0.0 mm Open ground · 600 m9 mph · gusts 16 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
70%
Moonrise
17:14 BST
Moonset
00:16 next morning BST

Views of the Moon may come and go through cloud breaks. 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)

300 m97/100 · very good
Wind / gust
8 mph / 14 mph
Typical / low
9.3°C / 9.1°C · much of the night
In cloud
0% of modelled night
Condensation
Low
600 m97/100 · very good
Wind / gust
9 mph / 16 mph
Typical / low
9.3°C / 9.1°C · much of the night
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.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Mixed65/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (65/100). Recent rain may leave seepage and damp rock, especially on shaded sections. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

Rock surfaceDry overhead; seepage uncertainPeak gust29 mphRain0.0 mm
Main concerndamp or incompletely dried rock possible
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Sunday 20 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

Confidence: Medium
Overall hill weather62/100Mixed
Wind5-20 mph westerly Gusts15-25 mph Feels like6 to 10°C PrecipitationUp to around 2 mm Cloud-free summit estimate45% Cloud base through day700-1,000 m Freezing levelAbove summit DaylightSunrise 06:59 · Sunset 19:17 · 12.3 hours daylight

The day on the hill

Frequent summit cloud on Y Llethr: summit wind broadly 5-20 mph, with gusts 15-25 mph at times (a moderate breeze).

Cloud & views

Cloud base mostly around 700–1000 m through daylight. 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.

Very little direct sunshine is likely, with extensive cloud. Drizzle is forecast at times.

The forecast total is up to around 2 mm, but local amounts will vary.

Rain & temperature

The ground is likely to be wet after recent rain.

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 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.

Morning · 08:00–12:00 Mixed Summit winds around 10-20 mph. Gusts around 15-25 mph are possible on exposed ground.
66/100
Afternoon · 12:00–17:00 Mixed Summit winds around 5-15 mph. Gusts around 15-25 mph are possible on exposed ground. Rain is forecast during this period.
57/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaCondensation risk is high near 300 and 600 m. 64/100Mixed · 600 m View detailsHide details
Night beginning Monday 21 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). Light winds are expected on open ground, though local shelter and exposure still matter. Little overnight rain is forecast. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain0.1 mm Open ground · 600 m11 mph · gusts 18 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
78%
Moonrise
17:38 BST
Moonset
01:32 next morning BST

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 21 Sep, 17:00 BST to 22 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
10 mph / 15 mph
Typical / low
12.1°C / 11.9°C
In cloud
0% of modelled night
Condensation
High
600 m64/100 · reasonable
Wind / gust
11 mph / 18 mph
Typical / low
12.1°C / 11.9°C
In cloud
0% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 8°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor27/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (27/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust18 mphRain0.5 mm
Main factorswet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Monday 21 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

Confidence: Medium
Overall hill weather62/100Mixed
Wind5-15 mph westerly Gusts10-20 mph Feels like8 to 12°C PrecipitationAround 2-5 mm Cloud-free summit estimate40% Cloud base through day600-900 m Freezing levelAbove summit DaylightSunrise 07:01 · Sunset 19:15 · 12.2 hours daylight

The day on the hill

Frequent summit cloud on Y Llethr: summit wind broadly 5-15 mph, with gusts 10-20 mph at times (light winds).

Cloud & views

Cloud base mostly around 600–900 m through daylight. 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.

Any sunshine may be confined to lower ground or breaks away from the summit.

Rain & temperature

Rain and drizzle are forecast at times. The forecast total is around 2-5 mm, but local amounts will vary.

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 Less than 1 hour 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
Less than 1 hour
Later
Less than 1 hour

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Mixed Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is forecast during this period.
62/100
Afternoon · 12:00–17:00 Mixed Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is forecast during this period.
62/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaAbout 2.6 mm is forecast, with rain possible around pack-up. 64/100Mixed · 600 m View detailsHide details
Night beginning Tuesday 22 September 2026

Full overnight outlook

Open-hillside camping looks reasonable overall around 600 m (64/100). Light winds are expected on open ground, though local shelter and exposure still matter. Around 2.6 mm is forecast, including rain around pack-up. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain2.6 mm Open ground · 600 m8 mph · gusts 19 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
86%
Moonrise
17:56 BST
Moonset
02:50 next morning BST

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 22 Sep, 17:00 BST to 23 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m64/100 · reasonable
Wind / gust
6 mph / 16 mph
Typical / low
12.1°C / 11.8°C
In cloud
0% of modelled night
Condensation
High
600 m64/100 · reasonable
Wind / gust
8 mph / 19 mph
Typical / low
12.1°C / 11.8°C
In cloud
0% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 8°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor27/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (27/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust17 mphRain2.0 mm
Main factorswet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Tuesday 22 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

Confidence: Medium
Overall hill weather35/100Poor
Wind15-25 mph northwesterly Gusts25-35 mph Feels like2 to 6°C PrecipitationAround 5-10 mm Cloud-free summit estimate55% Cloud base through day600-1,300 m Freezing levelAbove summit DaylightSunrise 07:02 · Sunset 19:13 · 12.2 hours daylight

The day on the hill

On Y Llethr: summit wind broadly 15-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Things to watch

Thunderstorms are possible from early morning into around midday. Keep an escape route from exposed ridges and descend if thunder develops.

If a thunderstorm develops, sudden gusts and heavy rain can change conditions quickly. Visibility may drop briefly in showers.

Cloud & views

Cloud base around 600–900 m through the morning, lifting to 1000–1300 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 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. Sunny spells are possible away from summit cloud, but may not reach the top while it is in cloud.

Drizzle is forecast at times, with some passing showers too. The forecast total is around 5-10 mm, but local amounts will vary.

Forecast models differ on summit wind strength: around 14-26 mph at walker height, with gusts 20-37 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. If clothing gets wet, you can cool more quickly.

Keep a dry warm layer protected. A low thunderstorm risk remains difficult to time precisely.

Cloud-free timing: Around 35% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 5.4 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.

Early
0 h
Midday
1.8 h
Later
3 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Poor Summit winds around 15-25 mph. Gusts around 25-35 mph are possible on exposed ground. Rain is forecast during this period. Rain is possible during the morning, but forecast models disagree on whether it will fall.
19/100
Afternoon · 12:00–17:00 Mixed Summit winds around 15-25 mph. Gusts around 20-30 mph are possible on exposed ground. Summit cloud is more persistent early in this period, with better prospects later. Rain is forecast during this period.
51/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaA broadly very good night on a well-chosen pitch. 92/100Excellent · 600 m View detailsHide details
Night beginning Wednesday 23 September 2026

Full overnight outlook

Open-hillside camping looks very good overall around 600 m (92/100). It may be breezy on open ground, with gusts near 20 mph. Little overnight rain is forecast.

Overnight rain0.0 mm Open ground · 600 m10 mph · gusts 21 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
92%
Moonrise
18:09 BST
Moonset
04:08 next morning BST

Views of the Moon may come and go through cloud breaks. 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)

300 m92/100 · very good
Wind / gust
8 mph / 18 mph
Typical / low
8.4°C / 8.1°C · much of the night
In cloud
0% of modelled night
Condensation
Low
600 m92/100 · very good
Wind / gust
10 mph / 21 mph
Typical / low
8.4°C / 8.1°C · much of the night
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.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Low thunderstorm risk. Avoid exposed rock if storms develop. Poor3/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (3/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder. Low thunderstorm risk, broadly from early morning into around midday. Avoid committing to exposed ground if storms develop.

Rock surfaceWet rock likelyPeak gust28 mphRain8.5 mm
Main factorslow thunderstorm risk on exposed groundwet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Wednesday 23 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

Confidence: High
Overall hill weather82/100Good
Wind15-30 mph southerly Gusts30-40 mph Feels like-2 to 2°C PrecipitationLittle or none Cloud-free summit estimate90% Freezing levelAbove summit DaylightSunrise 07:04 · Sunset 19:10 · 12.1 hours daylight

The day on the hill

On Y Llethr: summit wind broadly 15-30 mph, with gusts 30-40 mph at times (strong winds).

Wind & exposure

Much calmer lower down - generally 0-10 mph in the valley, rising towards the tops.

Cloud & views

Cloud base around 1000–1300 m in the morning, then around 1700–2000 m around midday and 1300–1600 m by late afternoon. The summit is likely to stay mostly clear.

Rain & temperature

Little or no rain is forecast. Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around -2 to 2°C in the wind.

Forecast models differ on summit wind strength: around 18-29 mph at walker height, with gusts 26-41 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Keep windproof and warm layers readily available.

Buffeting may affect balance on exposed ground, particularly near ridges and edges.

Cloud-free timing: Around 95% early, falling to around 80% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 9 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
4 h
Later
3 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Excellent Summit winds around 10-20 mph. Gusts around 20-30 mph are possible on exposed ground.
85/100
Afternoon · 12:00–17:00 Good Summit winds around 15-25 mph. Gusts around 20-30 mph are possible on exposed ground.
78/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaGusts near 35 mph make meaningful shelter important. 54/100Mixed · 600 m View detailsHide details
Night beginning Thursday 24 September 2026

Full overnight outlook

Open-hillside camping looks mixed overall around 600 m (54/100). Open-ground gusts may reach about 35 mph. Seek meaningful shelter. Peak gusts range from about 25 mph at 300 m to 35 mph at 600 m. Around 3 mm is forecast, including rain around pack-up. Pitches near 600 m may spend part of the night in cloud, bringing damp conditions and poor visibility while cloud is present. Condensation risk is high near 300 and 600 m. Ventilation will matter.

Overnight rain3.0 mm Open ground · 600 m21 mph · gusts 33 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 8°C or lower

Moon overnight

Waxing gibbous moon

Illuminated disc
97%
Moonrise
18:21 BST
Moonset
05:27 next morning BST

Cloud at the reference camping height may hide the Moon. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 24 Sep, 17:00 BST to 25 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m59/100 · mixed
Wind / gust
18 mph / 27 mph
Typical / low
11.7°C / 11.1°C
In cloud
0% of modelled night
Condensation
High
600 m54/100 · mixed
Wind / gust
21 mph / 33 mph
Typical / low
11.6°C / 11.1°C
In cloud
53% of modelled night
Condensation
High

Warmth planning: As a broad starting point, consider a 2-season bag with an ISO/EN comfort rating at or below about 8°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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Gusts near 30 mph may affect balance on exposed rock. Mixed65/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look fair (65/100). Some rock may still be damp or drying, especially on polished slabs and vegetated sections. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Gusts may reach about 30 mph. Crosswinds can make exposed ridges substantially more serious.

Rock surfaceDamp or dryingPeak gust32 mphRainPossible · 22%
Main factorsgusts around 30 mphdamp or incompletely dried rock possible
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Thursday 24 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

Confidence: Medium
Overall hill weather52/100Mixed
Wind5-25 mph northwesterly Gusts25-35 mph Feels like2 to 6°C PrecipitationAround 5-10 mm Cloud-free summit estimate40% Cloud base through day500-1,100 m Freezing levelAbove summit DaylightSunrise 07:06 · Sunset 19:08 · 12.0 hours daylight

The day on the hill

A wet day with extensive summit cloud on Y Llethr: summit wind broadly 5-25 mph, with gusts 25-35 mph at times (a fresh breeze).

Cloud & views

Cloud base around 500–800 m in the morning, lifting to 600–900 m around midday and 800–1100 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 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. Very little direct sunshine is forecast.

Drizzle is forecast for much of the day. The forecast total is around 5-10 mm, but local amounts will vary.

Forecast models differ on summit wind strength: around 14-31 mph at walker height, with gusts 19-43 mph.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Exposed tops may feel chilly in the wind.

A windproof layer will help, with an extra warm layer for stops. If clothing gets wet, you can cool more quickly.

Keep a dry warm layer protected. Summit wind could be roughly 14-31 mph, which changes how difficult exposed walking may feel.

Cloud-free timing: Around 30% early, improving to around 60% later.

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.

Morning · 08:00–12:00 Poor Summit winds around 10-20 mph early in the morning, easing to 5-15 mph later. Gusts around 25-35 mph are possible on exposed ground. Rain is forecast during this period.
49/100
Afternoon · 12:00–17:00 Mixed Summit winds around 5-15 mph. Gusts around 10-20 mph are possible on exposed ground. Rain is forecast during this period. Some forecast models bring rain during the afternoon, while others keep it mostly dry.
56/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaConditions look very good, but forecast uncertainty caps the grade at 82/100. 82/100Good · 600 m View detailsHide details
Night beginning Friday 25 September 2026

Full overnight outlook

Open-hillside camping looks promising overall around 600 m (82/100). Light winds are expected on open ground, though local shelter and exposure still matter. A little rain may coincide with pitching or packing up. Forecast models are not closely enough agreed for an exceptional grade. The grade is capped at 82/100.

Overnight rain0.4 mm Open ground · 600 m6 mph · gusts 14 mph Morning pack-upNo wet signal Sleeping-bag warmthISO comfort rating about 4°C or lower

Moon overnight

Near-full moon

Illuminated disc
99%
Moonrise
18:31 BST
Moonset
06:47 next morning BST

Views of the Moon may come and go through cloud breaks. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 25 Sep, 17:00 BST to 26 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m82/100 · promising
Wind / gust
5 mph / 12 mph
Typical / low
8.6°C / 7.7°C · much of the night
In cloud
0% of modelled night
Condensation
Low
600 m82/100 · promising
Wind / gust
6 mph / 14 mph
Typical / low
8.6°C / 7.7°C · much of the night
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 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.

Did this match your night?Share a quick observation to help improve this beta forecast.Give feedback

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Poor7/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look very poor (7/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Cloud may also make route-finding and retreat harder.

Rock surfaceWet rock likelyPeak gust28 mphRain6.3 mm
Main factorswet rock likelymuch of the route may be in cloud
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Friday 25 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

Confidence: Unavailable
Overall hill weather93/100Excellent
Wind0-10 mph southerly Gusts10-20 mph Feels like0 to 4°C PrecipitationLittle or none Cloud-free summit estimate90% Freezing levelAbove summit DaylightSunrise 07:07 · Sunset 19:05 · 12.0 hours daylight

The day on the hill

Little rain and limited summit cloud on Y Llethr: summit wind broadly 0-10 mph, with gusts 10-20 mph at times (light winds).

Cloud & views

Cloud base around 900–1200 m in the morning, then around 1300–1600 m around midday and 1200–1500 m by late afternoon. 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. Cold on exposed tops: air temperature broadly 2 to 6°C, feeling around 0 to 4°C in the wind.

Forecast models disagree markedly on summit wind strength. Check again nearer the time.

Forecast confidence

Cloud height remains uncertain, especially where it is close to summit level. Overall confidence is unavailable: insufficient comparable wind, rain guidance.

Cloud-free timing: Around 70% early, improving to around 95% later.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 11 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
2 h
Midday
4 h
Later
3 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Excellent Summit winds around 0-10 mph. Gusts around 5-15 mph are possible on exposed ground.
91/100
Afternoon · 12:00–17:00 Excellent Summit winds around 0-10 mph. Gusts around 5-15 mph are possible on exposed ground.
95/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaGusts near 40 mph make meaningful shelter important. 39/100Poor · 600 m View detailsHide details
Night beginning Saturday 26 September 2026

Full overnight outlook

Open-hillside camping looks poor overall around 600 m (39/100). A lower pitch near 300 m looks more comfortable. Conditions are less suitable by 600 m. Open-ground gusts may reach about 40 mph. Seek meaningful shelter. Peak gusts range from about 35 mph at 300 m to 40 mph at 600 m. Around 3.8 mm is forecast, including rain around pack-up. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain3.8 mm Open ground · 600 m15 mph · gusts 40 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Near-full moon

Illuminated disc
100%
Moonrise
18:42 BST
Moonset
Outside this window

Views of the Moon may come and go through cloud breaks. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 26 Sep, 17:00 BST to 27 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m59/100 · mixed
Wind / gust
13 mph / 33 mph
Typical / low
9.8°C / 8.4°C · much of the night
In cloud
0% of modelled night
Condensation
High
600 m39/100 · poor
Wind / gust
15 mph / 40 mph
Typical / low
9.2°C / 8.4°C · much of the night
In cloud
13% 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 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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaRock may be damp or still drying. Good78/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look good (78/100). Recent rain may leave seepage and damp rock, especially on shaded sections. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp.

Rock surfaceDry overhead; seepage uncertainPeak gust13 mphRain0.0 mm
Main concerndamp or incompletely dried rock possible
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Saturday 26 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

Confidence: Unavailable
Overall hill weather36/100Poor
Wind20-35 mph southwesterly Gusts35-45 mph Feels like4 to 8°C PrecipitationAround 10-20 mm Cloud-free summit estimate50% Cloud base through day700-1,000 m Freezing levelAbove summit DaylightSunrise 07:09 · Sunset 19:03 · 11.9 hours daylight

The day on the hill

A wet day on Y Llethr: summit wind broadly 20-35 mph, with gusts 35-45 mph at times (strong winds). Visibility may drop briefly in showers.

Wind & exposure

Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud-height uncertainty could put the summit in or out of cloud.

Clear spells may be difficult to time.

Cloud & views

Cloud may hang lower on southwestern slopes and lift somewhat on the northeastern side, but local terrain can differ. Drizzle is forecast for much of the day, with some passing showers too.

The forecast total is around 10-20 mm, but local amounts will vary. Forecast models disagree markedly on summit wind strength.

Check again nearer the time. Buffeting may affect balance on exposed ground, particularly near ridges and edges.

Forecast confidence

Overall confidence is unavailable: insufficient comparable wind, rain guidance.

Sunshine context Model-grid estimate, not summit sunshine

The surrounding model grid indicates 9.2 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
0.8 h
Midday
3.8 h
Later
2.9 h

Overnight forecast: 17:00–08:00 (UK local time), in Wild camping below.

Morning · 08:00–12:00 Poor Summit winds around 25-35 mph. Gusts around 35-45 mph are possible on exposed ground. Buffeting may affect balance on exposed ground, particularly near ridges and edges. Summit cloud is more persistent early in this period, with better prospects later. Rain is forecast during this period.
32/100
Afternoon · 12:00–17:00 Poor Summit winds around 20-30 mph. Gusts around 35-45 mph are possible on exposed ground. Buffeting may affect balance on exposed ground, particularly near ridges and edges. Rain is forecast during this period.
41/100

Compare an early start with later conditions. The main forecast above covers the day in more detail.

Overnight · 17:00–08:00Wild campingBetaAbout 15.3 mm is forecast, with rain liable to affect both pitching and packing up. 39/100Poor · 600 m View detailsHide details
Night beginning Sunday 27 September 2026

Full overnight outlook

Open-hillside camping looks poor overall around 600 m (39/100). It may be breezy on open ground, with gusts near 30 mph. Peak gusts range from about 25 mph at 300 m to 30 mph at 600 m. Roughly 15.3 mm is forecast overnight, with rain liable to affect both pitching and packing up. Condensation risk is high near 300 and 600 m, so a wet pack-up is possible. Ventilation will matter.

Overnight rain15.3 mm Open ground · 600 m17 mph · gusts 28 mph Morning pack-upDampness possible Sleeping-bag warmthISO comfort rating about 6°C or lower

Moon overnight

Waning gibbous moon

Illuminated disc
98%
Moonrise
18:53 BST
Moonset
Outside this window

Extensive cloud may limit moonlight. Illumination describes the sunlit part of the Moon, not brightness at your pitch.

Overnight window: 27 Sep, 17:00 BST to 28 Sep, 08:00 BST. Approximate open-horizon times; hills can hide the Moon. Still take a headtorch.

Elevation reference (open ground)

300 m39/100 · poor
Wind / gust
14 mph / 23 mph
Typical / low
9.8°C / 8.8°C · much of the night
In cloud
0% of modelled night
Condensation
High
600 m39/100 · poor
Wind / gust
17 mph / 28 mph
Typical / low
9.8°C / 8.8°C · much of the night
In cloud
0% 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 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

Approximate height is enough, please do not share an exact wild-camp location.

Daytime · exposed rockClimbing & scramblingBetaWet rock is likely. Gusts near 40 mph may affect balance on exposed rock. Poor25/100 View detailsHide details
Generic exposed-rock guidance

Full climbing & scrambling outlook

Conditions for exposed scrambling look poor (25/100). Rain during the climbing period is likely to leave rock wet and more slippery. The mapped summit rock is Mudstone (Hafotty Formation). Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Gusts may reach about 40 mph. Crosswinds can make exposed ridges substantially more serious.

Rock surfaceWet rock likelyPeak gust41 mphRain13.3 mm
Main factorsgusts around 40 mphwet rock likely
Mapped summit rock Mudstone Hafotty Formation
Origin
Sedimentary
Rock family
Slate or mudstone
Mapping
BGS Geology 50K · 1:50,000
Rock-response profile
Moderate confidence
View the summit BGS record

Often positive when dry, but smooth, polished or slabby sections can become markedly more slippery when damp. Summit-point bedrock mapping; the actual route may cross different rock, superficial deposits, polish, lichen or seepage.

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

A broad surface report is enough; you do not need to identify a particular route.

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.

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 Y Llethr on Sunday 27 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

Weather data: Open-Meteo (CC BY 4.0). Adapted by Mountain Weather.

Forecast run: 2026-09-20

Keep exploring

Weather around Y Llethr.

Compare the summit forecast with the wider regional picture and nearby peaks before choosing a route.

Regional mountain forecastEryri (Snowdonia)View area →
Rhinog Fach712 m · 1.3 km awayForecast →Diffwys750 m · 2.4 km awayForecast →Rhinog Fawr720 m · 3.3 km awayForecast →Y Garn629 m · 5.0 km awayForecast →

A forecast is part of the decision.

Mountain weather can differ sharply from conditions in the valley. Check official warnings, carry appropriate navigation and clothing, and be ready to change the plan. Read how Mountain Weather forecasts are produced and where their limits lie.

Choose another summit