Condition Analysis
AI-powered assessment using site data and 14-day weather history
The last significant rain was the 47.5mm deluge on April 11, followed by lighter showers on April 12 (7.8mm total, last drops around 16:00). Today (April 13) has been dry so far with moderate wind and dropping humidity — the exposed rhyolite should be drying, but given the enormous recent saturation (71mm in 7 days) and the 400m altitude, residual seepage and damp patches in sheltered spots are very likely. Climbers should visually inspect holds before committing.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Sheep Pen plateau sits at 400m and is frequently in cloud during unsettled spells; even on nominally dry days, hill fog can deposit moisture on the rock surface and prevent drying.
- The west-facing aspect means direct sun only arrives in the afternoon and evening — morning sessions may find rock that hasn't yet warmed or dried, particularly on north-facing facets of individual boulders.
- The exposed, perched position is a major asset today: the sustained wind (even at ~17 km/h from the south) will be actively stripping surface moisture from the non-porous rhyolite.
- After 47.5mm on April 11 alone, water will still be draining through the scree and cracks around boulder bases; lower problems and anything near seepage lines or drainage gullies may remain wet.
Warnings
2
- The 47.5mm deluge on April 11 may have left standing water and active seepage around boulder bases — approach with care on the steep scree, which will be slippery.
- Hill fog is possible at 400m today; if cloud descends, rock will re-wet rapidly and conditions will become unsafe — be prepared to retreat.
Reasoning
The rock received 47.5mm on April 11 and a further 7.8mm on April 12, with the last rain ceasing around 16:00 yesterday — giving roughly 20 hours of drying so far, which is marginal even for non-porous rhyolite at this altitude and humidity.
Moderate southerly wind (~17 km/h) on the exposed plateau and dropping humidity (74%) today are helping, but the west aspect limits direct solar warming to the afternoon, and overnight humidity was high (75–83%), meaning effective drying has only been occurring for a few hours this morning.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no risk of hold breakage from moisture — the concern is purely friction loss on damp surfaces.
Early spring at 400m in Snowdonia means cool temperatures (max ~9°C today), slow evaporation rates, and a real possibility of hill fog or low cloud re-wetting surfaces during the day.
Contributing Factors
7
71mm fell in the past 7 days including a massive 47.5mm event on April 11, saturating the ground and all drainage paths around the boulders.
No precipitation recorded today (April 13) and the forecast shows 0mm, giving the rock a full day to dry.
The perched, exposed position at 400m catches the 17 km/h southerly wind, accelerating surface drying on the non-porous rhyolite.
The rock does not absorb water, so surface moisture is the only concern and it evaporates relatively quickly once rain stops.
At 400m with a max of only 9°C and overnight lows near 4°C, evaporation rates are significantly lower than at valley-level crags.
Humidity at 74% and averaging 75% over the past week limits evaporative drying and risks condensation on cold rock surfaces.
Light showers fell until around 16:00 on April 12, and much of the intervening overnight period had high humidity (>75%), meaning effective drying time is limited.
Recommendations
3
- Visit in the afternoon when the west-facing rock has had maximum solar warming and wind exposure; morning conditions are likely to be damper.
- Carefully test friction on lower-angle holds before attempting steeper or committing problems — if smears feel greasy, back off and wait.
- Avoid problems near the base of boulders or below obvious seepage/drainage lines, as these will retain moisture longest after the recent heavy rain.
Previous Analyses
Do Not Climb
92%
2 days ago
Sheep Pen Boulders are almost certainly wet today following 47.5mm of heavy rain yesterday and a further 6.9mm today, with 70mm in the past week alone. Even with the site's exposed position, the rock will be saturated on the surface and extremely slippery — conditions are clearly unsuitable for climbing.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Yesterday's 47.5mm deluge was exceptional and will have left standing water, pooling on horizontal surfaces, and seepage across many of the boulders despite the exposed plateau position.
- The west-facing aspect receives only afternoon/evening sun in spring, and today's overcast SW-wind conditions mean minimal solar drying assistance.
- The scree approach will be wet and loose after sustained heavy rain — take extra care on the steep 15-minute hike even if just visiting to inspect conditions.
- At 400m altitude in early April, ambient temperatures around 5–9°C significantly slow evaporation rates compared to valley-floor crags.
Warnings
3
- Rhyolite becomes extremely slippery when wet — at this steep bouldering venue, a friction-dependent fall from height is a serious injury risk.
- The scree approach will be treacherous after sustained heavy rain; exercise extreme caution if visiting to assess conditions.
- Check BMC RAD for any peregrine or raven nesting restrictions at Ogwen Valley crags during the February–June nesting season.
Reasoning
The rock is almost certainly wet: 47.5mm fell yesterday followed by 6.9mm today, and there have been zero consecutive dry days — surface moisture will be widespread across all boulder faces.
Despite the exposed, wind-catching plateau position, the sheer volume of recent rainfall (70mm in 7 days) combined with today's continued precipitation, SW wind, and 80% humidity means meaningful drying has not occurred.
Rhyolite is non-porous and does not suffer structural weakening when wet, so there is no hold-breakage or rock-damage concern — the issue is purely friction and safety.
Early April at 400m in Snowdonia is still firmly in the unpredictable spring window; low temperatures (averaging 8°C), high humidity, and frequent Atlantic fronts make sustained drying periods rare.
Contributing Factors
6
47.5mm fell yesterday and 6.9mm today, with 70mm total in the past 7 days — the boulders will have widespread surface water.
There have been no consecutive dry days leading into today; the last meaningful dry spell ended on April 7th before 9.1mm on April 9th restarted the wet cycle.
The plateau's perched, exposed position catches strong winds (27 km/h today) which will aid surface evaporation, but this cannot overcome today's active rainfall.
Humidity has averaged 74% over the past week and is 80% today, significantly reducing the atmosphere's capacity to absorb moisture from rock surfaces.
Temperatures around 5–9°C at 400m altitude slow evaporation rates considerably compared to summer conditions.
The west-facing aspect only receives direct sun in the afternoon/evening, and overcast spring skies today further reduce any solar drying benefit.
Recommendations
3
- Do not visit today — the rock will be wet and dangerously slippery on these steep boulder problems.
- Monitor conditions through April 13–14; if the forecast 0.7mm on the 13th stays minimal and humidity drops, an afternoon visit on the 14th might be worth assessing on arrival, but a further 3.1mm is forecast.
- The next realistic window could open around April 17–18 if the forecast dries out as suggested — check updated forecasts closer to the date.
Do Not Climb
95%
3 days ago
With 37.7mm of heavy rain falling today on top of an already saturated week (54.5mm in 7 days, 150.2mm in 28 days), Sheep Pen Boulders will be thoroughly wet and completely unsuitable for climbing. The rock will have zero friction and seepage from the plateau will be active; there is no prospect of usable conditions today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The exposed plateau position catches strong southerly winds today (~39 km/h), which will help surface drying once rain stops, but cannot overcome 37.7mm of active precipitation.
- The hidden plateau above Ogwen Valley can hold standing water and seepage after heavy rain, and the scree approach will be treacherous in these saturated conditions.
- At 400m altitude with temperatures only reaching 6°C, evaporative drying is severely limited in early April — cloud base may be at or below crag level.
- West-facing aspect means afternoon sun could assist drying on subsequent days, but persistent SW/S weather systems will continue delivering moisture through the forecast period.
Warnings
3
- The steep scree approach to Sheep Pen Boulders will be dangerously slippery in current saturated conditions — risk of injury on the walk-in alone.
- Rhyolite loses almost all friction when wet; attempting steep boulder problems (V4–V12) on greasy rock poses a serious fall risk with no rope protection.
- Cloud base may be at or below 400m today given the heavy rain and low temperatures — navigation and visibility could be poor on the plateau.
Reasoning
The rock is currently soaking wet from 37.7mm of rain today, compounded by 54.5mm over the past 7 days and persistently high humidity, meaning every surface — including sheltered overhangs — will be saturated.
Despite strong southerly winds at this exposed site, active heavy rain today and continued light precipitation forecast for the next several days mean meaningful drying cannot begin for at least 24–48 hours.
Rhyolite is non-porous and does not suffer structural damage when wet, so hold integrity is not a concern, but friction on this volcanic rock drops dramatically when wet, making the steep problems extremely dangerous.
Early April at 400m in Snowdonia is a notoriously wet and cold period; the prolonged saturated spell (150mm in 28 days) reflects typical spring conditions, and low temperatures (6°C max today) severely limit evaporative drying.
Contributing Factors
6
37.7mm of rain today is the heaviest single-day total in the entire 28-day record, ensuring all rock surfaces are thoroughly drenched.
54.5mm in the last 7 days and 150.2mm in 28 days means the surrounding ground and any seepage sources are fully saturated.
Strong 39 km/h southerly winds would normally aid drying, but are irrelevant while rain is actively falling and humidity remains above 80%.
A maximum of only 6.2°C at 400m severely limits evaporative drying capacity, prolonging the time needed to dry rock surfaces.
Zero consecutive dry days heading into today means no drying window has been available, and the forecast shows continued light precipitation for the next 4 days.
Light rain is forecast for the next 4 days (1.7mm, 2.0mm, 3.4mm, 13.4mm) with no sustained dry spell in sight, preventing a proper drying window.
Recommendations
3
- Do not visit today — conditions are clearly unsafe with heavy rain and saturated rock offering zero friction.
- Monitor the forecast beyond April 17th for a potential dry window; at least 2 consecutive dry days with wind and temperatures above 10°C would be needed to consider a visit.
- If you do visit the Ogwen area, be aware the scree approach to Sheep Pen will be extremely slippery when wet — consider alternative indoor options in Llanberis.
Do Not Climb
85%
4 days ago
The rock is almost certainly wet today following 9.1mm of rain yesterday and 2.4mm today, with zero consecutive dry days. Although Sheep Pen Boulders is exposed and dries relatively quickly for a high-altitude venue, the ongoing precipitation and high humidity mean surface moisture will be present, making the rhyolite dangerously slippery.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Sheep Pen's perched, exposed plateau catches strong winds from all directions, which normally accelerates drying — but today's rain means the rock has not had time to benefit from this.
- At 400m with a west aspect, the boulders will be in cloud or mist during periods of low pressure, and the recent weather pattern has brought repeated frontal systems across Snowdonia.
- The steep scree approach from the Ogwen Valley will be slippery and loose in wet conditions, adding risk before you even reach the boulders.
- The recent wet spell (125mm in 28 days) means ground saturation is high; even sheltered overhanging faces may have seepage from above running down the rock.
Warnings
3
- Wet rhyolite is extremely slippery — friction loss on Borrowdale Volcanic / Ogwen rhyolite can be dramatic and lead to unexpected falls.
- The steep scree approach is hazardous in wet conditions; take extra care on the 15-minute ascent.
- Tomorrow (April 11th) is forecast to bring nearly 30mm of rain — do not plan a visit.
Reasoning
With 9.1mm yesterday and 2.4mm today, the rock surfaces are actively wet or at best damp; zero consecutive dry days confirms no meaningful drying window.
Despite strong 36 km/h southerly winds today, the ongoing precipitation and 72% humidity prevent effective drying of the west-facing boulders, especially at 400m altitude.
Rhyolite is non-porous and structurally sound when wet — there is no risk of hold breakage or rock damage, but friction loss on wet volcanic rock is severe.
Early April in Snowdonia at 400m is firmly within the unpredictable spring window; temperatures hovering around 8°C with persistent frontal rainfall make sustained drying periods rare.
Contributing Factors
7
2.4mm of rain today means surfaces are currently wet with no drying window.
9.1mm fell on April 9th, saturating all surfaces before today's additional rain.
There has been no uninterrupted dry spell to allow even surface drying on the rhyolite.
36 km/h southerly winds on the exposed plateau would speed drying if precipitation stopped, but cannot overcome active rainfall.
125mm in the last 28 days indicates persistent ground saturation and likely seepage even on non-porous rock.
Humidity is not extreme but is still elevated enough to slow evaporation at altitude, especially combined with cool temperatures.
The steep scree approach from Ogwen will be slippery and potentially hazardous after sustained wet weather.
Recommendations
3
- Do not visit today — the rock is wet and the rhyolite will be dangerously slippery.
- Monitor conditions for April 14th, which is the first forecast dry day with light winds and warmer temperatures, but verify on arrival.
- If visiting later this week, test friction carefully on low-consequence slabs before committing to steeper problems, and be aware of seepage lines from the saturated ground above.
Do Not Climb
45%
5 days ago
Today has 1.4mm of precipitation forecast following a very wet recent period (147.5mm in 28 days), and the rock had only two genuinely dry days (April 7–8) before today's renewed moisture. While the exposed position and wind help drying, high overnight humidity (91–93%) and today's rain mean surfaces are likely damp, and rhyolite friction will be compromised.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Sheep Pen's perched, exposed plateau catches wind from all directions, which significantly accelerates surface drying on non-porous rhyolite — but overnight cloud cover at 100% with humidity above 90% will have deposited condensation on the boulders.
- At 400m altitude in the Ogwen Valley, the site is frequently in or near cloud base during spring, meaning moisture can arrive as mist/condensation even without measurable rainfall.
- The W-facing aspect means the boulders only receive afternoon and evening sun, limiting solar drying during the shorter spring days; morning sessions will find colder, damper rock.
- The steep scree approach can be slippery and hazardous in wet or misty conditions — factor this into the overall risk assessment for today.
Warnings
2
- Rhyolite becomes very slippery when wet — friction loss on damp volcanic rock is severe and falls from even low boulder problems can cause serious injury.
- The scree approach to Sheep Pen is steep and exposed; in wet or misty conditions, take extra care and allow additional time.
Reasoning
After two dry days (April 7–8) the surface had largely dried, but overnight humidity of 91–93% with 100% cloud cover likely deposited condensation, and today's 1.4mm rain will re-wet exposed surfaces.
The 26.6 km/h SW wind today will help strip surface moisture from this exposed plateau, but with ongoing light rain and 79% humidity, effective drying is limited until the precipitation stops.
Rhyolite is non-porous and structurally unaffected by moisture — there is no risk of hold breakage or rock damage from climbing when damp, but friction loss on wet volcanic rock is significant.
Early April at 400m in Snowdonia is still firmly in the unsettled spring window; temperatures are marginal for efficient drying, and the site is vulnerable to rapid weather changes and lingering cloud.
Contributing Factors
6
1.4mm of precipitation today will wet boulder surfaces and prevent full drying despite wind.
Humidity above 90% with 100% cloud cover overnight likely deposited condensation on the boulders before today's rain.
The plateau's 26.6 km/h SW wind exposure accelerates surface drying on this non-porous rock once rain stops.
April 7–8 were completely dry with warm temperatures (up to 19°C) and low humidity on the 7th, which would have dried surfaces well before today's setback.
147.5mm over 28 days indicates a persistently wet spell, with seepage lines and ground saturation likely contributing ambient moisture around the boulders.
At 400m in early April, temperatures are cool (max 10.2°C today) and the site is prone to cloud immersion, limiting drying efficiency.
Recommendations
3
- Wait for a full dry day with wind before visiting — the forecast suggests April 13th may offer the best window if it stays dry as predicted.
- If you do visit today or tomorrow, bring a towel and be prepared to find damp rock; test friction carefully on easy problems before committing to harder lines.
- Check the BMC RAD for any bird nesting restrictions in the Ogwen area, as peregrine nesting season is well underway in April.
Marginal — Assess Conditions
70%
6 days ago
Two full dry days with warm temperatures (up to 19°C yesterday) and moderate wind on this exposed plateau should have dried the rhyolite surfaces well. However, today's humidity has risen to 82% and the preceding weeks have been very wet (148mm in 28 days), so sheltered nooks and seepage areas may retain dampness — a visual check on arrival is warranted.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The elevated, exposed plateau position catches wind from all directions, which significantly accelerates surface drying on this non-porous rhyolite — the site's key advantage after rain.
- At 400m with a W aspect, overnight cloud cover and rising humidity (82% today) can deposit condensation or light mist on rock surfaces, especially on the shaded east-facing sides of boulders in the morning.
- The steep scree approach means conditions at road level are not representative — cloud base can sit at or below 400m in spring, keeping the boulders damp even without rain.
- Some problems on the lower or north-facing sides of boulders are known to hold seepage longer after prolonged wet spells; the 148mm accumulated over the last month means these zones may still be damp.
Warnings
2
- Today's rising humidity and potential for low cloud at 400m could make surfaces greasy without warning — reassess conditions throughout your session.
- The forecast shows rain every day from April 9–13; this may be the last climbable window for nearly a week.
Reasoning
Surface moisture from the last rain (1mm on April 5, trace on April 6) should have evaporated given two dry days with warm temperatures and moderate wind, though today's 82% humidity suggests atmospheric moisture may be lingering.
The exposed W-aspect plateau with 15–30 km/h winds and temperatures reaching 19°C yesterday provided excellent drying conditions; rhyolite's non-porous nature means surface water evaporates quickly in such conditions.
Rhyolite does not absorb water and is not susceptible to structural weakening when wet — there is no risk of hold breakage from recent moisture.
Early April in Snowdonia is transitionally unpredictable; the recent warm spell is unusual, and humidity is now climbing with an incoming SW weather system forecast for tomorrow.
Contributing Factors
7
No meaningful precipitation since April 5 (1mm), with only a trace on April 6, giving approximately 48 hours of drying.
Yesterday reached 19.1°C with humidity as low as 38%, providing exceptional drying conditions for a 400m Snowdonian crag.
Consistent 20–30 km/h winds across the exposed plateau accelerate evaporation on the non-porous rhyolite surfaces.
Today's humidity has climbed to 82% (from 44% yesterday afternoon), which may cause condensation on rock surfaces and reduce friction.
148mm over 28 days is very wet even for Snowdonia; ground saturation means seepage and drainage lines on boulders may still be active.
4mm forecast for April 9 with continued unsettled weather through the week, so today represents a narrow window.
Rhyolite does not absorb water, so the primary concern is surface moisture and friction rather than structural damage.
Recommendations
3
- Head up early and visually check rock surfaces — feel for any greasy film or dampness, especially on north-facing and shaded boulder faces before committing to problems.
- Prioritise the most exposed and sun-catching (west/south-facing) boulder faces, which will have dried best; avoid any seepage lines or problems that feel polished or slick.
- Be aware this is likely a narrow weather window — rain returns tomorrow, so plan your session accordingly and bring layers for the exposed 400m position.
Marginal — Assess Conditions
65%
8 days ago
After a very wet week, today is the first fully dry day with improving conditions — dropping humidity (70%) and a moderate southerly breeze. The exposed plateau and non-porous rhyolite should have shed most surface moisture, but given heavy rain on April 4th (12.8mm) and only one full dry day since, some sheltered faces and seepage areas may still be damp; on-site assessment is essential.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The plateau's fully exposed position at 400m means wind-driven drying is very effective, but low cloud and mist can roll in quickly from the Ogwen Valley, re-wetting surfaces without actual rain.
- West-facing aspects won't receive direct sun until afternoon/evening, so morning sessions may find residual dampness on shaded or north-facing boulder faces.
- The scree approach can be treacherous when wet — recent heavy rain may have left the path slippery and loose, so extra care is needed on the 15-minute walk in.
- Some boulder problems at Sheep Pen have natural drainage channels and horizontal breaks that can hold seepage for days after prolonged wet spells like the recent one (161.5mm in 28 days).
Warnings
2
- The scree approach may be slippery after recent heavy rain — take care on the steep 15-minute walk in.
- At 400m, conditions can deteriorate rapidly if low cloud rolls in; be prepared to retreat if mist or drizzle develops.
Reasoning
Surface moisture from the 1mm on April 5th morning and 12.8mm on April 4th has had roughly 30+ hours of drying in moderate wind, but high background humidity (84% average over the last week) and 400m altitude limit evaporation rates.
The exposed plateau with 25–32 km/h winds and today's drop to 70% humidity should dry non-porous rhyolite surfaces effectively, though only one full dry day is marginal after 32mm in the preceding week.
Rhyolite is non-porous and does not suffer structural weakening when wet, so hold breakage is not a concern — the risk is purely friction-related.
Early April at 400m in Snowdonia is still firmly in the transitional spring period; overnight temperatures near freezing (3.7°C) and high humidity mean condensation and overnight dew are likely, and conditions can change rapidly.
Contributing Factors
7
32.1mm fell in the last 7 days including 12.8mm on April 4th, with only one dry day since — seepage lines and sheltered areas may still hold moisture.
Zero precipitation today with humidity dropping to 70% and a moderate 26 km/h southerly wind provides solid drying conditions.
The fully exposed 400m plateau catches all available wind, significantly accelerating surface drying on this non-porous rock.
Rhyolite does not absorb water, so drying is a surface-only process and can occur within hours under favourable conditions.
Average humidity of 84% over the past week and overnight readings near 88% limit evaporation and may cause condensation on cold rock surfaces.
West-facing boulders won't receive direct sun until mid-afternoon, meaning morning conditions may be damper than afternoon.
Overnight lows of 3.7°C at the valley floor likely translate to near or below freezing at the 400m plateau, risking frost and condensation on rock surfaces.
Recommendations
3
- Visit in the afternoon when the west-facing boulders have had maximum sun and wind exposure; test friction carefully on easier problems before committing to harder lines.
- Bring a towel and soft boar's hair brush to dry any residual surface moisture, but avoid climbing if seepage is visible on problems.
- Check the BMC RAD for any bird nesting restrictions in the Ogwen area — peregrine nesting season is active through June.
Do Not Climb
70%
9 days ago
The Sheep Pen Boulders have had a very wet recent period with 32.7mm in the last 7 days including 12.8mm yesterday and 1.3mm today, leaving zero consecutive dry days. Despite the exposed, windy position that aids drying, the persistent rainfall, high humidity (85% average), and cool spring temperatures mean surfaces are very likely still damp and friction will be compromised.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The plateau's exposed position and strong westerly winds (32 km/h today) will accelerate surface drying significantly compared to sheltered valley crags, but the lack of any dry spell undermines this advantage.
- At 400m altitude with temperatures around 5°C, condensation and lingering dampness in cracks and textured holds is likely even when surfaces appear dry to the eye.
- The west-facing aspect means the boulders only receive afternoon and evening sun, limiting solar drying hours during the early spring when the sun angle is still relatively low.
- The scree approach can be treacherous when wet — loose volcanic scree on steep ground becomes slippery, adding risk even before reaching the boulders.
Warnings
2
- Rhyolite friction drops dramatically when damp — falls from friction loss on steep boulder problems at this grade (V4–V12) carry serious injury risk.
- The steep scree approach is hazardous in wet conditions; take extra care on descent.
Reasoning
With 12.8mm yesterday, 7.6mm the day before, and 1.3mm today, the rock surfaces are almost certainly still wet or at least damp in textured areas, seepage lines, and sheltered faces.
Strong westerly winds (32 km/h) on the exposed plateau will strip surface moisture relatively quickly on exposed faces, but with only partial drying windows between repeated rainfall events, the rock has not had a meaningful dry-out period.
Rhyolite is non-porous and does not suffer structural weakening when wet — there is no risk of hold breakage or rock damage from climbing on damp volcanic rock.
Early April at 400m in Snowdonia is still firmly in the unpredictable spring window with cool temperatures, frequent Atlantic fronts, and limited solar heating — conditions that significantly slow drying.
Contributing Factors
7
32.7mm over the last 7 days with rain on 6 of those 7 days means the rock has had no sustained drying window.
Light rain today means surfaces are freshly wet with zero consecutive dry days.
The exposed plateau at 32 km/h westerly wind strips surface water efficiently from this non-porous rock.
Low temperatures at 400m altitude reduce evaporation rates and prolong damp conditions in sheltered spots.
Persistently high humidity over the past week limits evaporation even on windy, exposed surfaces.
West-facing boulders only catch afternoon sun, and in early April the sun angle provides limited drying power at 400m.
Volcanic rock does not absorb water so only surface moisture needs to evaporate, meaning recovery is fast once rain stops.
Recommendations
3
- Wait for at least one full dry day with wind before visiting — tomorrow (April 6) still shows light rain, but April 7 looks much more promising with 0mm, 16°C, and lower humidity.
- If you do visit, bring a towel and brush to test friction on lower problems before committing to anything at height — the textured rhyolite can feel deceptively grippy while still damp.
- Check the scree approach carefully as it will be slippery after recent rain; consider approach shoes rather than trainers.
Do Not Climb
85%
10 days ago
Sheep Pen Boulders are currently wet from today's 6.2mm of rain on top of a very wet recent period (34mm in the last 7 days, 154mm in the last 28 days). With zero consecutive dry days and high humidity, the rock will be slippery and conditions are unsuitable for bouldering today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The exposed plateau position and strong southerly winds (39 km/h today) will help strip surface moisture relatively quickly once rain stops, but the rock is actively wet right now.
- The west-facing aspect means afternoon sun is available for drying, but early April sun angles are still low and drying power is limited at 400m altitude.
- Seepage lines and pooling in scoops between boulders are common after prolonged wet spells — even when surfaces appear dry, hidden moisture can persist in cracks and on landings.
- At 400m in the Ogwen Valley, low cloud and mist frequently envelop the plateau in these conditions, adding ambient moisture even between rain showers.
Warnings
2
- Wet rhyolite is extremely slippery — bouldering falls from even moderate height onto wet rock and saturated ground pose serious injury risk.
- The steep scree approach to Sheep Pen can be treacherous in wet conditions; take extra care on the descent.
Reasoning
The rock is currently wet from today's 6.2mm rainfall, compounded by 34mm over the past week and persistently high humidity (85–93% recent days), meaning surfaces will be thoroughly damp.
Strong southerly winds (39 km/h) on this exposed plateau will aid surface drying, but with rain falling today and zero consecutive dry days, meaningful drying has not yet begun.
Rhyolite is non-porous and does not suffer structural weakening when wet — the risk is entirely friction-related and safety-based rather than rock conservation.
Early April at 400m in Snowdonia means limited solar heating, cool temperatures (max 9.5°C today), and the site is in the heart of the wet spring season with frequent Atlantic weather systems.
Contributing Factors
7
6.2mm of precipitation today means the rock is actively wet with no drying window yet.
34mm in the last 7 days and 154mm over 28 days indicate saturated ground and persistent ambient moisture around the boulders.
There has been no meaningful dry period to allow surface and seepage drying.
Average humidity of 86% over the past week severely impedes evaporation even on exposed rock.
38.9 km/h southerly winds on this exposed plateau will accelerate surface drying once rain ceases.
A maximum of 9.5°C at 400m altitude provides limited thermal energy to drive evaporation.
Rhyolite does not absorb water so only surface moisture needs to evaporate, which is faster than porous rock types.
Recommendations
3
- Do not visit today — the rock is actively wet and friction on rhyolite is severely compromised in these conditions.
- Target April 7th or later when a multi-day dry spell with warmer temperatures (up to 17°C) and lower humidity (68%) should produce genuinely good conditions.
- If visiting during the drying window, check shaded north-facing faces of boulders and any seepage lines carefully before committing to problems.
Do Not Climb
90%
11 days ago
Sheep Pen Boulders are currently wet and unsafe for climbing. Today has seen nearly 12mm of rain with 91% humidity, following a very wet week (32.7mm in the last 7 days), and the rock will have no meaningful drying time before dark.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The exposed plateau position catches strong SW winds which aid drying, but today's rain is ongoing and wind direction is feeding moisture directly onto the west-facing boulders.
- At 400m altitude in early April, temperatures are marginal and cloud base frequently sits at or below the plateau, keeping the rock damp even between showers.
- The west aspect means afternoon sun can assist drying, but with persistent cloud cover and rain today there will be no solar gain to help.
- Seepage from the saturated ground and surrounding peat/scree can keep the base of some boulders and lower holds damp long after surface moisture has evaporated.
Warnings
2
- Wet rhyolite is extremely slippery — friction loss is severe and falls from even low-height boulder problems can cause serious injury on the rocky landing zones.
- The steep scree approach to Sheep Pen Boulders will be treacherous in wet conditions — take extra care on the ascent and descent.
Reasoning
The rock is actively wet today with 11.9mm of precipitation, 91% humidity, and zero consecutive dry days — surface moisture will be present on all faces.
Despite strong winds (29.9 km/h SW), the west-facing aspect is directly exposed to the moisture-laden prevailing wind, and there has been no dry period since the last significant rain to allow any drying.
Rhyolite is non-porous and does not suffer structural damage when wet, so there is no hold-breakage concern.
Early spring at 400m in Snowdonia means low sun angle, frequent cloud immersion, and cool temperatures (average 6.7°C over the past week) that significantly slow evaporation.
Contributing Factors
7
11.9mm of precipitation today means the rock is currently wet with no prospect of drying before end of day.
32.7mm in the last 7 days and 158.2mm in the last 28 days have kept the ground saturated and seepage lines active.
Humidity at 91% today and averaging 85% over the past week severely inhibits surface evaporation on the rock.
The exposed plateau and 29.9 km/h winds would normally aid rapid drying on this non-porous rock, but cannot overcome active rainfall.
Rhyolite does not absorb water, so once rain stops and conditions improve the surface will dry relatively quickly.
The prevailing SW wind drives moisture directly onto the west-facing boulders, maximising wetting and minimising shelter.
Averaging only 6.7°C over the past week at 400m, evaporative drying is slow even when rain pauses.
Recommendations
3
- Do not visit today — the rock is actively wet and friction on rhyolite will be dangerously low.
- Monitor conditions for April 6th, which is forecast to be dry with lower humidity (69%) and could offer the first realistic window after sufficient drying.
- Check BMC RAD for any bird nesting restrictions at Sheep Pen Boulders before planning a visit, as the peregrine and raven nesting season is now active.
Climbing Outlook