Condition Analysis
AI-powered assessment using site data and 14-day weather history
Light rain fell yesterday (2.5mm) and today has seen only a trace (0.3mm), but high humidity (avg 80% over the last week) and limited sunshine at 400m mean surface moisture may linger in sheltered spots. The exposed, wind-swept plateau and non-porous rhyolite favour quick drying, so a morning climbing window before the light afternoon drizzle looks plausible — but visual assessment on arrival is essential.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The plateau sits at 400m and can be in cloud even when the Ogwen Valley below is clear, which keeps surfaces damp and kills friction despite the rock being nominally dry.
- The west-facing aspect means direct sun only arrives in the afternoon/evening; morning sessions rely on wind and ambient warmth for drying.
- The exposed, perched position is a double-edged sword — excellent for wind-drying but also catches passing showers and hill fog that won't show in valley forecasts.
- Some boulder problems have sheltered undersides or north-facing facets that hold seepage and condensation longer than the main west-facing surfaces.
Warnings
3
- Heavy rain (10.8mm) is forecast tomorrow — do not plan a session on May 8th.
- At 400m the plateau may be in cloud today despite valley conditions looking acceptable; be prepared to abort.
- Light drizzle is forecast from 14:00–15:00 today; retreat or stop climbing if surfaces become slick mid-session.
Reasoning
Yesterday's 2.5mm and today's trace precipitation, combined with persistent high humidity (73–94% over recent days), suggest residual surface moisture is likely on sheltered faces, though exposed surfaces may be dry.
Moderate wind (~14–18 km/h) and the exposed plateau position aid drying, but the west aspect receives no direct sun until afternoon, and at 400m temperatures are only ~11°C, so evaporation is sluggish.
Rhyolite is non-porous and structurally unaffected by moisture; the only risk is reduced friction on damp surfaces, not hold breakage.
Early May in Snowdonia brings highly variable conditions at altitude — hill fog, sudden showers, and cool temperatures are common, and the recent week has been wetter and cooler than late April's dry spell.
Contributing Factors
6
2.5mm fell yesterday and 0.3mm today, with 3.3mm the day before; though individually light, the cumulative effect on a high-altitude site with high humidity is significant.
Humidity has averaged 80% over the past seven days, inhibiting evaporation and potentially causing condensation on cold rock surfaces at 400m.
The plateau catches all available wind (14–18 km/h today), which significantly aids surface drying of non-porous rhyolite.
Rhyolite does not absorb water, so only surface moisture matters — and it can evaporate within hours given adequate wind and warmth.
The hourly forecast shows no precipitation until 14:00, offering a potential 5–6 hour dry window from mid-morning if the rock has shed overnight moisture.
10.8mm is forecast for May 8th, which will reset any drying progress and make conditions poor for the next several days.
Recommendations
3
- If climbing today, arrive mid-morning to take advantage of the dry window before light drizzle arrives around 14:00; test friction on an easy problem first.
- Bring a towel and brush — sheltered faces and horizontal surfaces may hold residual dampness that can be cleared on non-porous rock.
- Consider postponing if cloud is sitting on the plateau on arrival, as hill fog will keep all surfaces slick regardless of forecast precipitation.
Previous Analyses
Do Not Climb
35%
2 days ago
Rain is falling today (3.3mm across the afternoon) on top of light showers over the past few days, and humidity is high at 400m; the rock is likely damp or will become so. With more rain forecast through the week, conditions are not suitable for climbing today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- At 400m on the Glyderau plateau, the boulders are frequently in cloud when humidity exceeds ~80%, meaning condensation can keep surfaces damp even without direct rainfall.
- The exposed, perched position is excellent for wind-drying, but today's light and variable winds (under 15 km/h) offer limited drying benefit.
- The W-facing aspect means the boulders only receive afternoon and evening sun — with 100% cloud cover forecast all afternoon today, solar drying is negligible.
- The steep scree approach can be slippery in wet conditions; take extra care on the descent if surfaces are greasy.
Warnings
2
- The volcanic rock becomes extremely slippery when wet — friction-dependent slab and face problems are dangerous in these conditions.
- At 400m, the boulders may be in cloud today and through much of this week; visibility and condensation can be worse than valley weather suggests.
Reasoning
Light but persistent precipitation over the past week (0.5mm on May 5, 3.3mm on May 3, 2.4mm on May 2, 2.1mm on May 1) has kept the rock intermittently wet, and today's 3.3mm of afternoon rain will re-wet surfaces.
The single fully dry day (May 4) with moderate northerly wind would have cleared surface moisture, but renewed showers on May 5 and today have re-dampened the rock, and the W aspect receives no useful sun under today's overcast skies.
Rhyolite/BVS volcanic rock is non-porous and does not suffer structural damage from moisture, so hold breakage is not a concern.
Early May at 400m in Snowdonia is still cool (averaging ~10°C) with high humidity, and drying rates are significantly slower than summer; cloud-base frequently sits at or below boulder altitude.
Contributing Factors
6
Over 3mm of rain is forecast between 12:00 and 17:00 today, directly wetting the rock surface during prime climbing hours.
Light rain on four of the last six days has prevented the rock from fully drying out between events.
Humidity averaging 81% today at 400m altitude means evaporation is slow and condensation on rock is likely.
The plateau's exposed position usually promotes rapid drying, though today's light winds (5–14 km/h) are below their usual strength.
BVS rhyolite does not absorb water, so once surface moisture evaporates the rock is immediately climbable without a long drying-out period.
10.8mm on May 9 and 19.7mm on May 10 will thoroughly soak the site, resetting any drying progress.
Recommendations
3
- Wait for a sustained dry spell — the next realistic window may be May 12 onward if the forecast holds dry after May 11.
- If you visit in the coming days, carry a towel and brush but be prepared to walk away if surfaces feel greasy or slick.
- Check live mountain weather forecasts (MWIS for Snowdonia) on the day, as conditions at 400m can differ markedly from valley-level forecasts.
Marginal — Assess Conditions
70%
3 days ago
The rock has had two full dry days since light rain on May 3rd (3.3mm), and the exposed, wind-swept position should have cleared surface moisture. However, high humidity (79–94%) and persistent cloud cover at 400m altitude raise the possibility of condensation or residual dampness on the rock, so an on-site check is advisable before committing to harder problems.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- At 400m on the Ogwen plateau, the boulders can sit in cloud even when the valley is clear — today's 90–100% cloud cover through the morning may deposit condensation on rock surfaces.
- The west-facing aspect means direct sun only arrives in the afternoon/evening; combined with today's clearing skies from ~15:00 onward, the best friction window is likely mid-to-late afternoon.
- The perched, exposed position catches the northerly wind (currently ~15–17 km/h) effectively, which is the primary drying mechanism today given the limited sunshine.
- The 3.3mm rain on May 3rd was preceded by a very wet April (113mm over 28 days); while rhyolite is non-porous, seepage and drainage lines around boulder bases may still hold moisture.
Warnings
2
- At 400m the boulders may be in cloud during the morning — do not assume conditions match the valley floor; reassess on arrival.
- The steep scree approach can be slippery in damp conditions; take care on the 15-minute walk in.
Reasoning
Surface moisture from May 3rd's 3.3mm rain should have largely evaporated over two dry days, but persistent high humidity (84–94%) and cloud immersion at altitude may maintain a thin film of condensation on the rock.
The exposed position and moderate northerly wind (~15–17 km/h) provide good drying potential, but the west aspect receives no direct sun until afternoon and today's clearing skies only arrive from ~15:00, meaning effective drying is concentrated in a narrow late-afternoon window.
Rhyolite is non-porous and suffers no structural weakening from moisture — there is zero hold-breakage risk from the recent wet period.
Early May at 400m in Snowdonia means temperatures are still cool (5–9°C), overnight condensation and cloud immersion are common, and conditions can feel wintry despite the calendar — friction is noticeably poorer in cool, humid air.
Contributing Factors
6
No measurable rain since May 3rd (3.3mm), giving 48+ hours for surface moisture to clear from non-porous rhyolite.
Humidity has been 79–94% over the past 24 hours at altitude, raising the risk of condensation forming on cold rock surfaces.
The plateau catches the current northerly wind at ~15–17 km/h, which actively strips surface moisture and aids drying.
At 400m with 95–100% cloud cover through the morning, the boulders may be sitting in mist, depositing moisture directly onto rock.
Cloud cover drops to 43–63% from 15:00 onward with humidity falling to 64–68%, creating a promising late-afternoon friction window.
Temperatures of 7–9°C are typical for May at this altitude and won't impair friction if the rock is dry, but slow evaporation compared to summer.
Recommendations
3
- Target the afternoon window from approximately 15:00 onward when cloud cover and humidity are forecast to drop significantly, offering the best friction.
- Test friction carefully on lower-grade problems before committing to anything hard — if the rock feels greasy or chalked holds appear damp, back off.
- Bring a towel and brush; some sheltered faces or lower boulder bases may retain moisture from recent high humidity even if the main faces feel dry.
Marginal — Assess Conditions
62%
4 days ago
Yesterday saw 3.3mm of rain with very high humidity (94%) and persistent cloud at 400m altitude, but today is dry with moderate northerly winds that should progressively dry the rock through the morning and afternoon. By midday the exposed plateau position and improving conditions should have cleared surface moisture from most faces, but some sheltered or north-facing surfaces may remain damp — a visual check on arrival is essential.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- At 400m the plateau can sit in cloud even when valleys are clear, and yesterday's 94–100% humidity likely kept surfaces saturated with condensation well beyond when rain stopped.
- The exposed, perched position above Ogwen Valley is a significant advantage — the northerly wind today (up to 16 km/h) will sweep across the plateau and accelerate surface drying on the non-porous rhyolite.
- West-facing problems will not receive direct sun until mid-afternoon, so friction on shaded faces may remain compromised into the early afternoon despite the drying wind.
- The steep scree approach means conditions on the plateau can differ markedly from the valley — what feels dry in Ogwen may still be damp at the boulders.
Warnings
2
- At 400m altitude, cloud can roll in rapidly and re-wet surfaces with no warning — monitor conditions throughout your session.
- The prolonged wet spell (113mm in 28 days) means ground and seepage areas around boulder bases may be boggy; take care on landings.
Reasoning
Rain ceased around 06:00 yesterday morning (3.3mm total, mostly overnight), but humidity remained above 90% through much of yesterday and into the early hours today, meaning surfaces likely stayed damp or condensation-wet until this morning.
Today's dry conditions with moderate northerly wind on this exposed plateau should clear surface moisture from the non-porous rhyolite within a few hours of humidity dropping below 80%, which appears to be happening from mid-morning onwards.
Rhyolite is non-porous and does not absorb water, so there is no structural risk or hold-breakage concern — the issue is purely friction.
Early May at 400m in Snowdonia brings cool temperatures and frequent cloud immersion; drying is slower than summer, and overnight condensation can re-wet surfaces that dried during the day.
Contributing Factors
6
3.3mm fell yesterday (mostly overnight into early morning of May 3rd) with only ~24 hours of drying since, though no further rain has fallen since.
Humidity has been 80–94% for the past 36 hours and remains around 78–81% today, slowing evaporation and potentially allowing condensation on cool rock surfaces at 400m.
The site's exposed, perched position catches the northerly wind (up to 16 km/h today), which is the primary drying mechanism for this non-porous rock.
No precipitation is forecast for the remainder of today, with humidity gradually dropping to the low 70s by late afternoon and evening, giving continuous drying.
West-facing boulders won't receive direct sun until mid-to-late afternoon, relying solely on wind for drying through the prime morning and early afternoon climbing hours.
The volcanic rock does not absorb moisture, so once surface water evaporates the friction returns fully — no extended internal drying period is needed.
Recommendations
3
- Aim for an afternoon session (after 13:00) to maximise drying time — by then the wind will have had several hours to clear surface moisture and humidity should be dropping.
- Test friction carefully on arrival by feeling holds and attempting easy warm-up problems before committing to harder lines; if rock feels greasy or slick, wait or move on.
- Carry a towel and soft brush to clear any residual dampness from holds, but be prepared to walk away if conditions are not right — the approach is short enough to justify a reconnaissance trip.
Do Not Climb
55%
4 days ago
Today has seen 3.3mm of rain with very high humidity (92%) and light winds, meaning the rock is likely wet or at least damp right now. Although rhyolite dries quickly in good conditions, the current combination of cloud, moisture, and light northerly wind at 400m makes reliable surface drying unlikely today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The exposed plateau position normally aids rapid drying, but today's light 13 km/h northerly wind and 92% humidity severely limit evaporation.
- At 400m with a north wind, the crag may be sitting in or near cloud base, which would keep surfaces persistently damp regardless of whether active rain has stopped.
- The west-facing aspect means the boulders receive no direct sun until afternoon/evening, further delaying any drying from today's rain.
- The preceding week (Apr 26–May 2) was relatively dry with only ~4.5mm of light showers, so seepage from deeper in the rock mass is unlikely — today's concern is purely surface moisture.
Warnings
2
- Rhyolite becomes very slippery when wet — the primary risk today is friction loss leading to unexpected slips on the boulders.
- At 400m with 92% humidity, hill fog or low cloud may envelop the plateau, keeping rock persistently damp even if rain has stopped.
Reasoning
3.3mm fell today on top of 2.1mm and 2.4mm over the previous two days, and with humidity at 92% at 400m altitude, the rock surface is almost certainly wet or greasy right now.
Light 13 km/h northerly wind and overcast skies with extreme humidity mean evaporative drying is minimal; the west aspect receives no sun until late afternoon, so meaningful drying is unlikely before evening.
Rhyolite is non-porous and does not suffer structural damage from moisture — there is no risk of hold breakage or surface degradation from climbing today.
Early May in Snowdonia can bring persistent low cloud and hill fog at 400m, and temperatures around 11°C provide only moderate drying potential even when skies clear.
Contributing Factors
6
Active or very recent precipitation today means surface moisture is present on the rock.
Humidity at 92% at 400m altitude dramatically slows evaporation and suggests possible low cloud or mist enveloping the crag.
Unusually light wind for this normally exposed site reduces the drying advantage the plateau usually provides.
Volcanic rhyolite does not absorb water, so only surface moisture needs to clear — no structural damage risk from climbing on damp rock.
West-facing boulders receive no direct sun until afternoon, delaying drying after this morning's rain.
The extended dry spell from Apr 21–30 means there is no deep seepage concern; the issue is today's fresh surface moisture only.
Recommendations
3
- Wait until tomorrow (May 4th) when a dry day with moderate northerly wind should allow the rock to dry fully by late morning.
- If you do visit today, carry a towel and be prepared to find conditions too greasy for safe bouldering — retreat without climbing if holds feel slick.
- Target afternoon sessions on dry forecast days this week to maximise the benefit of the west-facing aspect catching late sun.
Do Not Climb
45%
4 days ago
Today has seen 3.2mm of rain with 90% humidity and light northerly winds at 400m altitude — the rock is very likely still wet or damp right now. Although rhyolite dries quickly in good conditions, the combination of ongoing precipitation, high humidity, and relatively light wind today means surface moisture will linger.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Sheep Pen's exposed plateau position normally aids rapid drying, but today's light 14 km/h northerly wind and 90% humidity severely limit evaporation at 400m.
- The W-facing aspect means afternoon/evening sun could help, but with cloud cover implied by the high humidity, solar drying contribution today is likely minimal.
- The 15-minute scree approach means conditions cannot be easily checked from below — committing to the walk-in without confidence the rock is dry risks a wasted trip.
- After a very wet mid-April (47.5mm on the 11th alone plus persistent follow-up rain), some seepage lines on lower boulder faces may still be active despite the drier late-April spell.
Warnings
2
- Rhyolite becomes very slippery when wet — attempting steep boulder problems on damp rock poses a genuine fall risk.
- At 400m with northerly winds and temperatures around 7–12°C, conditions can feel significantly colder than the valley; dress for mountain weather.
Reasoning
With 3.2mm of rain today and 90% humidity, surface moisture is almost certainly present on the boulders right now.
Light wind (14.4 km/h from the N) on a W-facing exposed plateau at 400m provides limited drying; the high humidity means evaporation will be very slow through the rest of today.
Rhyolite is non-porous and does not suffer structural damage when wet — the concern is purely friction loss on damp surfaces.
Early May in Snowdonia at 400m can still see cool, damp conditions with cloud sitting on the tops; spring weather is changeable and humidity often stays elevated at altitude.
Contributing Factors
6
Active precipitation today means the rock surface is currently wet or has been wet very recently.
At 90% humidity, evaporation is extremely slow and the rock will feel greasy even where not visibly wet.
Wind is well below the site's typical exposure levels, reducing the plateau's usual advantage of rapid wind-drying.
Rhyolite does not absorb water, so once surface moisture evaporates the rock will be fully functional — no extended internal drying needed.
The elevated, open position will aid drying once humidity drops and wind picks up, but today's conditions limit this benefit.
Modest recent rainfall but today's contribution keeps the cumulative picture damp; the earlier dry spell from Apr 21–30 was beneficial but has now been interrupted.
Recommendations
3
- Wait for tomorrow (May 4th) which is forecast dry with lower humidity — arrive after midday to allow any residual moisture to evaporate.
- If you do visit today, carry alternative plans for the Ogwen Valley as the boulders are very likely to be greasy.
- Check conditions visually on arrival tomorrow — if the rock feels cool and clammy to the touch, wait for wind and sun to do their work before committing to hard problems.
Do Not Climb
35%
4 days ago
Today has seen 3.1mm of rain with 90% humidity and light winds — the rock is almost certainly wet right now. Although rhyolite dries relatively quickly, the combination of ongoing precipitation, very high humidity, and light northerly winds (sheltering the west-facing boulders) means surfaces are unlikely to be in good condition today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The west-facing aspect means today's northerly wind provides little direct drying benefit to the boulder faces, reducing the site's normally excellent wind-drying advantage.
- Sheep Pen sits at 400m on an exposed plateau which, while great for drying in favourable winds, also means it is frequently in or near cloud base during high-humidity spring days like today.
- The steep scree approach takes ~15 minutes and will be slippery in current damp conditions — factor this into your plans and allow extra time.
- Despite a good dry spell from April 21–30, the last three days (May 1–3) have brought ~7.6mm of rain with persistently high humidity, resetting the drying clock.
Warnings
2
- Rhyolite becomes extremely slippery when wet — friction-dependent boulder problems are dangerous in current conditions.
- The scree approach will be slick in the wet; take extra care if visiting to assess conditions.
Reasoning
With 3.1mm of rain today and 90% humidity, rock surfaces are almost certainly wet or heavily damp right now.
Light 12 km/h northerly winds offer minimal drying to west-facing rock, and the extremely high humidity prevents effective evaporation.
Rhyolite is non-porous and does not suffer structural damage when wet — the concern here is purely friction loss and climber safety on slippery surfaces.
Early May at 400m in Snowdonia remains cool and prone to low cloud and persistent dampness; spring conditions can be slow to improve at altitude.
Contributing Factors
6
Active precipitation today means rock surfaces are currently wet and unsafe for high-friction bouldering.
Humidity at 90% effectively stalls evaporative drying, keeping surfaces damp even where not directly rained on.
The light wind from the north provides minimal drying benefit to these west-facing boulders, negating the site's usual wind-drying advantage.
Rhyolite does not absorb water, so once rain stops and conditions improve, drying will be relatively quick — but that hasn't happened yet today.
Rain on May 1 (2.1mm), May 2 (2.4mm), and May 3 (3.1mm) with high humidity means there has been no meaningful drying window.
The exposed position normally aids drying but at 400m it also means the boulders are likely in or near cloud base today given the humidity.
Recommendations
3
- Do not climb today — the rock is wet from today's rain and conditions are not suitable for safe bouldering on rhyolite.
- Tomorrow (May 4) is forecast dry with similar humidity; if winds pick up and humidity drops through the day, afternoon conditions may improve enough to warrant an on-site assessment.
- The best window this week looks to be May 6–7, when two consecutive dry days with dropping humidity should provide genuinely dry conditions — plan accordingly.
Marginal — Assess Conditions
55%
5 days ago
Today has seen 2.6mm of rain with high humidity (82%), so the rock is likely damp right now. However, rhyolite at this exposed, wind-swept plateau dries quickly, and the preceding week (Apr 21–30) was exceptionally dry — the rock had no deep saturation going into this wet spell. If rain has stopped and wind picks up, surfaces could dry within hours, but conditions need on-site verification.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Sheep Pen's perched plateau position above the Ogwen Valley is highly exposed to wind from all directions, which significantly accelerates surface drying even in cool, humid conditions.
- The steep scree approach takes ~15 minutes and conditions at the boulders can differ markedly from the valley floor — cloud and mist at 400m are common in spring and can keep surfaces damp even without rain.
- The west-facing aspect means afternoon and evening sun is the primary drying agent; morning visits after overnight dampness may find residual moisture on holds.
- Some boulder faces are overhanging or sheltered by adjacent blocks, and these steep problems may dry faster as they shed water quickly — worth checking these first on arrival.
Warnings
2
- Rhyolite becomes very slippery when wet — the exceptional friction this rock provides in dry conditions disappears completely with even a thin film of moisture, making falls on slabs and lower-angle problems likely.
- Cloud or mist engulfing the plateau at 400m can re-dampen surfaces quickly even after drying — be prepared to stop climbing if visibility drops.
Reasoning
Today's 2.6mm of rain on top of yesterday's 2.1mm means surface moisture is present, though the rock itself is non-porous and was thoroughly dried out during the exceptional dry spell from April 21–30.
Wind at 16.6 km/h from the south is moderate for this exposed plateau, and with the W aspect receiving afternoon sun, surfaces should dry within a few hours of rain ceasing — but humidity at 82% slows evaporation.
Rhyolite is non-porous and extremely hard; there is no risk of structural damage or hold breakage from recent moisture.
Early May in Snowdonia is transitional — days are lengthening and temperatures are mild (~14°C today), but cloud cover at 400m remains common and can suppress drying; no frost risk at current temperatures.
Contributing Factors
7
2.6mm today and 2.1mm yesterday mean fresh surface moisture is present on the rock right now.
The perched, exposed position catches wind effectively, and 16.6 km/h from the south will help clear surface moisture once rain stops.
Rhyolite does not absorb water, so only surface moisture needs to evaporate — no extended internal drying period required.
Elevated humidity significantly slows evaporation and increases the chance of condensation or lingering dampness on rock surfaces at 400m.
Nine consecutive dry days from April 21–29 with low humidity thoroughly dried the rock, meaning only the last two days' light rain needs to clear.
If skies clear at all this afternoon, the west-facing boulders will receive direct sun which aids drying considerably.
At 400m above the Ogwen Valley, the boulders can sit in low cloud, keeping surfaces damp even when rain has stopped.
Recommendations
3
- Wait until afternoon to allow any morning rain to clear and give the wind time to dry surfaces — check holds for greasy residue before committing to problems.
- Prioritise steep and overhanging problems first, as these shed water fastest and are most likely to be dry.
- Bring a towel and brush; if surfaces feel even slightly slick, back off — rhyolite friction drops dramatically when damp and the consequences on boulder problems are immediate.
Marginal — Assess Conditions
60%
6 days ago
After an excellent dry spell from April 20–30, today's 2.7mm of rain has broken the run, and the rock will need a few hours of wind and air movement to dry. The exposed plateau position and non-porous rhyolite mean surface moisture should clear relatively quickly, but with moderate southerly winds and 67% humidity, a visual check on arrival is essential before committing to problems.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Sheep Pen's perched plateau position at 400m catches wind from all directions, making it one of the fastest-drying bouldering venues in the Ogwen area — but at this altitude it is also frequently in cloud, which can re-wet apparently dry rock.
- The west-facing aspect means afternoon and evening sun only; on a May afternoon the boulders should receive direct sunlight from roughly 2pm onwards, aiding drying from today's rain.
- The steep scree approach means conditions can differ significantly from what you see in the valley — cloud base in the Ogwen Valley is often around 400–500m in spring, so the boulders may be shrouded even when the valley looks clear.
- Some problems on the lower or more sheltered sides of boulders may retain surface moisture longer, particularly any features with horizontal breaks or scoops that pool water.
Warnings
2
- Rhyolite becomes very slippery when wet — do not attempt friction-dependent slabs or mantels if any surface moisture remains.
- Check BMC RAD for any seasonal bird nesting restrictions at or near Sheep Pen Boulders before visiting.
Reasoning
Today's 2.7mm rain on non-porous rhyolite will sit as surface moisture; prior to today the rock had been essentially dry for 11+ consecutive days with very low humidity, so there is no deep saturation concern.
With 22 km/h southerly winds and the exposed plateau position, surface water on the rhyolite should evaporate within a few hours, though the west aspect won't receive direct sun until the afternoon.
Rhyolite is non-porous and extremely hard — there is no risk of structural damage or hold breakage from today's light rain or the preceding wet period.
Early May in Snowdonia brings lengthening days and reasonable temperatures (~15°C), but cloud base can still sit at or below 400m and spring showers are frequent; the forecast suggests an unsettled week ahead.
Contributing Factors
7
2.7mm of precipitation today has broken an 11-day dry spell and will leave surface moisture on the boulders.
Zero or trace precipitation from April 20–30 with low humidity and strong winds means the rock was thoroughly dry going into today.
The fully exposed 400m plateau catches all available wind, greatly accelerating surface drying on non-porous rock.
Moderate humidity will neither dramatically slow nor accelerate drying but is not ideal.
West-facing boulders will receive direct afternoon sun from ~2pm, helping evaporate any remaining surface moisture.
The next five days show repeated light rain (0.6–4.7mm daily) with high humidity (77–97%), suggesting conditions will deteriorate from tomorrow.
At 400m altitude in spring, the boulders may sit in or near the cloud base, re-wetting surfaces even between rain events.
Recommendations
3
- If visiting today, wait until mid-to-late afternoon to allow the morning rain to dry — the west aspect and wind exposure should clear surface moisture by then.
- Check the cloud base before making the steep approach; if cloud is sitting at or below 400m, conditions on the plateau will likely be damp regardless of valley conditions.
- The forecast turns increasingly unsettled from tomorrow — today may be the best window this week, so if you're set on climbing, prioritise steeper overhanging problems where water runs off fastest.
Likely Safe to Climb
90%
9 days ago
Sheep Pen Boulders have had three consecutive dry days following a prolonged dry spell from April 21–26, with today bringing strong SE winds (41 km/h) and low humidity (48%). The non-porous rhyolite at this exposed, wind-scoured plateau should be thoroughly dry and offering excellent friction.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The plateau's fully exposed position at 400m catches today's strong SE winds, which will have stripped any residual surface moisture very effectively.
- The last meaningful rain was 0.1mm on April 26 — essentially negligible — with truly wet weather ending on April 20 (1mm), giving over 8 days of effective drying.
- High overnight humidity (83–89%) on April 28 at this altitude may have deposited light condensation on some surfaces, but today's strong wind and low humidity will clear this quickly.
- Some north-facing or deeply recessed boulder faces may hold residual dampness from overnight condensation; assess shaded holds before committing to harder problems.
Warnings
1
- Strong winds (41 km/h) on the exposed plateau may affect balance on high problems and make spotting less effective — exercise caution on tall or exposed boulder problems.
Reasoning
The rock has been effectively dry for over a week, with only a trace 0.1mm on April 26 breaking an extended dry spell since April 20, and today's 48% humidity and 41 km/h winds ensure any residual surface moisture is gone.
The west-facing aspect means afternoon/evening sun exposure, and the strong SE wind today provides excellent cross-ventilation across the exposed plateau, making drying conditions near-optimal for this site.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no risk of hold breakage from moisture.
Late April conditions are favourable with lengthening days, moderate temperatures (15°C today), and the extended dry spell from April 21–26 provided an unusually good drying window for spring in Snowdonia.
Contributing Factors
6
Only 0.1mm of rain in the last 9 days, with the last significant rainfall (5.4mm) on April 17, providing ample drying time for non-porous rock.
40.7 km/h SE winds across this fully exposed plateau will rapidly clear any surface moisture or condensation.
Humidity at 48% is well below the threshold for condensation concerns, supporting excellent friction on the rhyolite.
Humidity reached 83–89% overnight on April 28 with light winds, but today's conditions will have cleared any condensation by mid-morning.
A forecast high of 15.4°C with strong sunshine aids evaporation and makes for comfortable bouldering conditions.
137.5mm over 28 days is substantial, but on non-porous rhyolite with 9 days of near-zero rainfall since, this has no residual impact on surface conditions.
Recommendations
3
- Conditions are excellent today — head up and enjoy the friction; the strong wind will keep the rock dry but bring a windproof layer for the exposed plateau.
- Check any deeply shaded or north-facing boulder surfaces for residual condensation before committing, especially early in the day.
- Be aware that the forecast deteriorates from May 2 onward with rain and high humidity, so today and tomorrow represent the best window this week.
Climbing Outlook