Condition Analysis
AI-powered assessment using site data and 14-day weather history
Today has seen 0.6mm of rain with very high humidity (89%), and the forecast shows continued light precipitation and elevated humidity through the week, culminating in a heavy 21mm event on Aug 18. While the rock enjoyed a good dry spell from Aug 11–13, today's moisture and the unsettled outlook make current conditions unreliable for friction-dependent bouldering.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Cromlech Boulders sit roadside in the Llanberis Pass, which can funnel cloud and mist even when surrounding areas are clear, keeping humidity high and surfaces damp.
- Jerry's Roof and the steeper problems can retain seepage and condensation on holds tucked under overhangs, even when vertical faces appear dry.
- The SW/W aspect means the boulders benefit from afternoon sun when available, but today's NW wind and cloud cover limit solar drying.
- Being a roadside venue at 250m in the Pass, low cloud and orographic drizzle are common and may not appear in weather station data — always check conditions on arrival.
Warnings
2
- Rhyolite friction drops dramatically when wet — falls from seemingly easy problems are a real risk on damp rock.
- A major rain event (21mm) is forecast for Aug 18; avoid climbing that day entirely.
Reasoning
Today's 0.6mm of rain combined with 89% humidity means rock surfaces are likely damp or at least not reliably dry, despite the preceding three dry days.
The excellent drying spell of Aug 11–13 (warm, dry, southerly winds) would have dried the rock thoroughly, but today's return of moisture with light NW winds at only 14 km/h has likely re-wetted surfaces and condensation is probable at this humidity.
Rhyolite is non-porous and does not suffer structural damage from moisture, so hold breakage is not a concern.
Mid-August in Snowdonia is peak summer but the Atlantic influence means unsettled spells with high humidity are common, and the coming week looks particularly wet.
Contributing Factors
5
0.6mm precipitation today with 89% humidity will leave surfaces damp and friction compromised on the rhyolite.
Aug 11–13 were warm and dry with southerly winds, which would have thoroughly dried the rock before today's moisture arrived.
Light rain forecast for Aug 15–17 followed by a significant 21mm event on Aug 18 means no sustained drying window in the coming days.
The exposed position in the Pass means wind-assisted drying is effective when precipitation stops, potentially allowing brief dry windows.
Humidity is forecast to remain above 80% through the week, which slows surface drying and promotes condensation on cool rock.
Recommendations
3
- Wait for a clearer window — the rock could dry within a few hours of sunshine and breeze, so monitor conditions closely if you're in the area.
- If you do visit, test friction on easy low problems first before committing to anything committing or high; the rhyolite becomes treacherously slippery when damp.
- Consider the heavy rain forecast for Aug 18 — plan any sessions before then or wait until at least Aug 20 when conditions may improve.
Previous Analyses
Likely Safe to Climb
90%
2 days ago
The Cromlech Boulders are dry today after three consecutive dry days with warm temperatures and moderate winds on an exposed SW/W aspect. Conditions are excellent for climbing this afternoon, though rain is forecast from tomorrow onwards so today is the best window for the foreseeable future.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside in the Llanberis Pass and are SW/W facing, receiving strong afternoon sun which has aided drying over the past three warm, dry days.
- Jerry's Roof and other overhanging problems may retain seepage from the recent wet spell (25–28 July) in cracks above, so check holds before committing to steeper lines.
- The venue is extremely popular and will be crowded on a sunny summer day — expect queues on classic problems and be courteous with pad placement.
- Humidity is forecast to rise sharply this evening (90%+ by 9pm) and rain arrives tomorrow, so the best friction window is this afternoon before conditions deteriorate.
Reasoning
Three consecutive dry days (Aug 11–13) with warm temperatures (24–30°C) and low humidity (51–62%) have thoroughly dried the non-porous rhyolite surfaces after the last trace rain on Aug 10.
The SW/W aspect and exposed position have received strong solar radiation and consistent wind, providing excellent drying conditions — surface moisture from the minor 0.1mm on Aug 10 would have evaporated within hours.
Rhyolite is non-porous and does not suffer structural weakening when wet; no hold breakage risk from recent moisture.
Mid-August is peak summer season with long daylight hours and generally favourable temperatures, though the Atlantic weather pattern is now bringing a wetter spell from tomorrow.
Contributing Factors
5
No measurable rain since Aug 10 (0.1mm trace), with warm temps up to 30°C and low humidity ensuring thorough surface drying.
The south-westerly aspect receives strong afternoon sun which accelerates drying on this exposed roadside venue.
Humidity today is 49–62% through the afternoon, providing excellent friction conditions on the crystalline rhyolite.
2.7mm forecast for Aug 14, followed by further rain including a major 54.5mm event on Aug 17, meaning today is the last good window.
Humidity rises above 80% after 8pm tonight with full cloud cover, which will reduce friction and may cause condensation on rock surfaces.
Recommendations
3
- Climb this afternoon for the best conditions — friction will be excellent in the warm, dry, sunny weather before humidity rises this evening.
- Wrap up your session by early evening as humidity climbs above 80% after 8pm and friction will noticeably decrease.
- Plan around this window: the next five days look wet with a very heavy rain event forecast for Aug 17, so today is likely the last good opportunity for nearly a week.
Likely Safe to Climb
92%
3 days ago
The Cromlech Boulders are in excellent condition today — two full dry days following only trace precipitation, with warm temperatures up to 30°C, low humidity (49%), and a favourable SW aspect ensuring thorough drying. Tomorrow also looks superb, but a deteriorating front arrives from August 14th onward.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside in the Llanberis Pass and their SW/W aspect catches afternoon sun well, which has been maximised by today's clear skies and 30°C temperatures.
- Some overhanging problems and north-facing surfaces (e.g. the back of certain boulders) can retain seepage or condensation longer, so check holds on shaded faces individually.
- The venue gets extremely crowded on warm summer days — with conditions this good and temperatures this high, expect competition for popular problems like Jerry's Roof.
- Light drizzle on Aug 9–10 (0.5mm total) was negligible and would have evaporated within hours given subsequent drying conditions.
Warnings
1
- Temperatures reaching 30°C may cause sweaty hands that reduce friction on slopers — chalk up frequently and consider climbing in the cooler morning or evening hours.
Reasoning
Only 0.5mm of precipitation fell in the last 7 days (trace amounts on Aug 9–10), followed by two completely dry days including today's exceptional 30°C heat, leaving the rhyolite surface thoroughly dry.
The SW/W aspect has received strong solar radiation over the past two days, and even moderate winds (17–22 km/h) at this exposed site would have evaporated any surface moisture from the trace rain within hours.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no hold-breakage risk from recent moisture.
Mid-August in a warm spell provides near-optimal conditions with long daylight hours and warm temperatures, though the forecast suggests a significant frontal system arriving from August 14th.
Contributing Factors
5
No measurable precipitation since Aug 10 (0.1mm trace), giving ample time for the non-porous rhyolite to shed all surface moisture.
Today's 30°C maximum with 49% humidity and clear skies provides outstanding evaporation conditions rarely seen at 250m in Snowdonia.
The SW/W-facing boulders catch direct afternoon sun and the exposed site benefits from consistent wind, accelerating surface drying.
Only 0.5mm fell in the last 7 days — far too little to cause any lingering moisture issues on non-porous rock.
Heavy rain forecast from Aug 14–17 (up to 36.7mm) will end this window of good conditions within two days.
Recommendations
3
- Climb today and tomorrow to make the most of this excellent window before the frontal system arrives on August 14th.
- Arrive early or late to avoid both the midday heat (30°C can make friction feel greasy from sweaty fingers) and peak crowds.
- Bring plenty of water — the roadside location offers no shade and conditions will be unusually hot for the Pass.
Marginal — Assess Conditions
70%
5 days ago
The Cromlech Boulders received significant rain on Aug 4–5 (21.2mm combined) but have had four mostly dry days since, with only trace precipitation; the SW/W aspect and exposed position should have cleared surface moisture by this afternoon. However, a trace of rain overnight (0.1mm) and high early-morning humidity (90%+) mean some dampness may linger in sheltered spots, so a visual check on arrival is warranted.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside in the Llanberis Pass and catch funnelled winds from the SW/W, which accelerates drying but also channels mist and drizzle through the pass.
- Jerry's Roof and other overhanging problems can harbour residual seepage and drips even when vertical faces appear dry — check underside holds carefully.
- The pass can trap low cloud and morning condensation at 250m altitude, so early-morning sessions may encounter damp rock even after dry spells.
- This is peak summer season and the boulders get extremely crowded on weekends — chalk residue on damp holds can create a dangerously slippery paste.
Warnings
1
- Rhyolite becomes very slippery when wet — do not attempt slab or friction-dependent problems if any dampness is detected on the surface.
Reasoning
The heavy rain on Aug 4–5 (21.2mm) was followed by four dry days with moderate winds and dropping humidity, so surface moisture from that event should be largely gone, though the 0.1mm trace overnight and high morning humidity may leave a slight film.
The SW/W aspect receives good afternoon solar radiation in August, and the exposed, wind-funnelled position in the pass means surface drying is efficient — four dry days after the main rainfall is ample for non-porous rhyolite to shed surface water.
Rhyolite is non-porous and does not suffer structural weakening when wet; hold breakage or rock damage from moisture is not a concern here.
Mid-summer provides the longest daylight hours and warmest temperatures for drying, though the recent cooler spell (15–17°C) and elevated humidity (75–88%) have slowed evaporation compared to the hot spell earlier in July.
Contributing Factors
5
21.2mm fell on Aug 4–5, a substantial soaking, though four subsequent dry days have allowed considerable drying on non-porous rock.
No significant precipitation since Aug 5 (only traces of 0.1–0.2mm), giving ample time for exposed rhyolite surfaces to dry.
0.1mm at midnight and humidity reaching 99% overnight may have left condensation or a damp film on the rock surface this morning.
The south-westerly aspect catches afternoon sun and the exposed pass position channels wind across the boulders, promoting rapid surface drying from midday onward.
Humidity drops to 58–62% by early afternoon with light winds and partial sun, creating a good drying window from roughly noon onwards.
Recommendations
3
- Visit from midday onward today when humidity drops below 65% and any overnight condensation has burned off.
- Physically touch holds on both sunny and shaded faces before committing to a problem — rhyolite friction drops dramatically with even a thin moisture film.
- Check overhanging features like Jerry's Roof for residual drips or seepage before attempting, as these sheltered areas dry last.
Marginal — Assess Conditions
70%
5 days ago
The Cromlech Boulders received significant rain on August 4–5 (21.2mm combined) but have had three fully dry days since, with today showing only a trace (0.1mm). The SW/W aspect and exposed position should have cleared surface moisture from most faces, but recent high humidity and the trace rain today warrant a visual check on arrival.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside below Dinas Cromlech and can channel water run-off from the hillside above, meaning some problems — particularly roof and overhang features like Jerry's Roof — may retain seepage even after the faces have dried.
- The SW/W aspect catches afternoon sun well in summer, which accelerates drying on the main faces, but north-facing sides of the boulders and shaded recesses will dry much more slowly.
- The Llanberis Pass funnels wind effectively, which helps surface drying but can also channel low cloud and mist, raising ambient moisture unexpectedly.
- This is the busiest bouldering venue in North Wales — weekend crowds polish chalk into damp patches, reducing friction; visiting midweek or early morning gives both better conditions and less queueing.
Warnings
1
- Rhyolite friction drops dramatically when wet — a surface that looks dry can still be slippery if there is a thin moisture film; test holds before committing to committing moves.
Reasoning
Three full dry days since the heavy rain of August 4–5 (21.2mm), combined with moderate winds and SW/W exposure, should have dried most surfaces, though today's trace precipitation and 76% humidity may leave a light film on some holds.
The SW/W aspect receives good afternoon solar radiation in August, and the exposed, wind-funnelled position in the Llanberis Pass accelerates evaporation — three dry days is typically sufficient for non-porous rhyolite surfaces to clear after moderate rain.
Rhyolite is non-porous and extremely hard; there is no risk of structural weakening or hold breakage from the recent wet spell.
Mid-summer provides long daylight hours and reasonable temperatures (high teens), though the recent cooler, humid spell with temps around 16–17°C and humidity in the 76–88% range has slowed drying compared to the warm, dry spell earlier in July.
Contributing Factors
6
Over 21mm fell across two days, the largest wet event in four weeks, saturating surfaces and potentially leaving seepage in cracks and overhangs.
August 6–8 were completely dry with moderate winds, providing adequate time for exposed rhyolite surfaces to shed surface moisture.
A trace of 0.1mm today means surfaces may not be perfectly dry right now, though this amount evaporates quickly on exposed rock.
The south-westerly aspect catches afternoon sun and the exposed pass position ensures good airflow, both favouring rapid surface drying.
Humidity has remained above 75% for much of the past week, slowing evaporation and potentially leaving a moisture film on shaded holds.
Rhyolite does not absorb water, so the concern is purely surface friction rather than structural damage — drying times are measured in hours, not days.
Recommendations
3
- Visit in the afternoon when the SW/W-facing surfaces have had maximum sun exposure and any morning dampness has evaporated.
- Test friction carefully on a low, easy problem before committing to harder lines — rhyolite becomes noticeably slippery with even a thin moisture film.
- Avoid shaded north-facing sides of the boulders and overhanging features where seepage from the Aug 4–5 rain may still be present.
Likely Safe to Climb
85%
6 days ago
The Cromlech Boulders have had three full dry days with moderate winds and decreasing humidity after the heavy rain on August 4–5, and today is dry with 67% humidity — excellent conditions for rhyolite to have shed all surface moisture. The rock should be dry and offering good friction right now.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The SW/W aspect means the boulders catch afternoon and evening sun well in summer, accelerating drying after the recent wet spell.
- Roadside location in the Llanberis Pass can funnel wind effectively, but the pass orientation means NW winds (as seen recently) may create localised sheltered spots where seepage persists on some problems.
- Jerry's Roof and other overhanging problems may retain residual dampness on holds tucked into horizontal breaks or beneath overlaps, even when vertical faces are dry.
- Weekend crowding can be intense at this venue — midweek sessions offer better conditions for working harder problems.
Reasoning
Three consecutive dry days following 21.2mm of rain on August 4–5, with today's humidity dropping to 67%, means surface moisture on this non-porous rhyolite should be fully evaporated.
The SW/W aspect combined with exposed wind (16–21 km/h from W and SW over recent days) provides strong drying; rhyolite surfaces at this aspect would dry within hours of rain ceasing, and three days is more than sufficient.
Rhyolite is non-porous and does not suffer structural weakening when wet, so hold breakage risk is negligible.
Mid-summer conditions with reasonable temperatures (15–20°C) and lengthening dry spells between fronts provide a good window; no freeze-thaw concerns at this time of year.
Contributing Factors
5
No precipitation since August 5, giving non-porous rhyolite ample time to shed all surface moisture.
Today's 67% humidity is notably lower than the 76–88% range of recent days, aiding final surface drying.
SW/W-facing boulders in an exposed position with moderate southerly winds today promote efficient evaporation.
21.2mm fell over two days, but three dry days with wind on non-porous rock means this is no longer a concern for surface conditions.
2.3mm forecast for August 9 will re-wet surfaces, narrowing today's optimal window.
Recommendations
3
- Climb today (August 8) to take advantage of the current dry window before rain returns tomorrow.
- Inspect holds on overhanging problems and beneath overlaps for residual dampness before committing to harder moves.
- Carry a towel and soft brush — some sheltered holds may have light condensation from the recent high-humidity days.
Marginal — Assess Conditions
72%
7 days ago
The Cromlech Boulders have had two full dry days following a wet spell that dropped over 21mm in the preceding week, and with the SW/W aspect and exposed position, surface moisture should have largely evaporated. However, humidity remains moderately high and some sheltered faces or undercuts may still hold dampness, so a visual check on arrival is warranted.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside in the Llanberis Pass which can funnel damp westerly air, meaning humidity can linger even on nominally dry days.
- Jerry's Roof and other overhanging problems with horizontal breaks can trap seepage and condensation long after the last rain.
- The SW/W aspect receives good afternoon sun in summer which accelerates surface drying on the main faces, but north-facing sides of the boulders will dry significantly slower.
- The site is at 250m in Snowdonia where orographic cloud and drizzle can occur without registering as measurable precipitation — conditions may be damper than weather data suggests.
Warnings
1
- Rhyolite becomes very slippery when wet — test friction carefully on each hold before committing to moves, especially on slabs and smears.
Reasoning
Two consecutive dry days after 21mm+ of rain in the prior week, combined with high humidity (74–86%), means surfaces are likely dry but some residual dampness could persist in sheltered spots and cracks.
The exposed position and SW/W aspect with moderate winds (17–28 km/h) favour rapid surface drying on rhyolite, and two dry days should be sufficient for most open faces, though undercuts and shaded surfaces may lag.
Rhyolite is non-porous and does not suffer structural weakening when wet — there is no risk of hold breakage from recent moisture.
Mid-summer provides long daylight hours and reasonable solar radiation for drying, though the recent cooler-than-average temperatures (15–17°C) and elevated humidity slow evaporation compared to the warm dry spell earlier in July.
Contributing Factors
6
Over 21mm fell between Aug 4–5, a significant amount that saturated surfaces and filled cracks just two days ago.
No precipitation on Aug 6–7 with moderate winds allows exposed rhyolite surfaces to shed moisture relatively quickly.
Humidity has remained 74–88% over recent days, slowing evaporation and potentially causing condensation on cooler rock faces.
The boulders' south-westerly aspect catches afternoon sun and the exposed position ensures consistent airflow, both aiding drying.
Rhyolite does not absorb water so there is no risk of structural damage, and surface moisture clears faster than on porous rock types.
Temperatures around 16–18°C are adequate but not exceptional for driving evaporation in the current humid conditions.
Recommendations
3
- Visit in the afternoon when the SW/W-facing surfaces have had maximum sun exposure and inspect each problem for dampness before committing.
- Avoid shaded, north-facing sides of the boulders and horizontal breaks or roofs where moisture may linger.
- Bring a towel and consider alternative problems if your target is in a sheltered or seepage-prone area.
Marginal — Assess Conditions
60%
9 days ago
Heavy rain on Aug 4–5 (21.2mm combined) was followed by a dry but overcast and humid day today; the exposed SW/W aspect and moderate wind should have dried surface moisture, but persistent high humidity and cloud cover through most of today may have slowed evaporation. Conditions are likely improving through the afternoon as humidity drops and cloud breaks, but a visual check on arrival is essential.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Cromlech Boulders sit roadside in the Llanberis Pass and can collect runoff and seepage from the hillside above, particularly after multi-day wet spells like the recent one.
- The SW/W aspect means the boulders receive afternoon and evening sun when cloud breaks — today's clearing from 15:00 onward should help dry remaining surface dampness.
- Jerry's Roof and other steep/overhanging problems may have stayed drier during the rain, but slab and lower-angle faces will have taken longer to shed moisture.
- The venue gets extremely crowded on summer weekends — midweek visits like today offer better conditions for patience-testing drying checks.
Warnings
2
- Rhyolite becomes very slippery when wet — do not attempt friction-dependent slab problems if any surface dampness remains.
- More light rain (1.9mm) is forecast for tomorrow (Aug 7), so today's late-afternoon window may be the best opportunity before conditions reset.
Reasoning
After 21.2mm of rain over Aug 4–5, followed by one dry but overcast and humid day (80% avg humidity), surface moisture has likely evaporated from exposed faces but damp patches may persist in sheltered recesses and seepage lines.
The W wind at ~23 km/h today on this exposed SW/W-facing venue aids drying considerably, but near-constant cloud cover and humidity above 80% until mid-afternoon have limited solar-driven evaporation — conditions improve significantly from 15:00 as humidity drops to the 60s.
Rhyolite is non-porous and does not suffer structural weakening when wet; the only risk is reduced friction on damp surfaces.
Mid-summer provides long daylight hours and reasonable temperatures for drying, though the recent unsettled spell with high humidity is typical of a Welsh August and slows surface drying compared to the warm dry spell earlier in July.
Contributing Factors
6
21.2mm fell on Aug 4–5, with only one full dry day since before today.
No rain today with sustained W winds of 17–23 km/h helping strip surface moisture from the exposed boulders.
Humidity remained above 80% through late morning with full cloud cover, limiting evaporation until the afternoon.
Humidity drops to the 60s from 15:00–19:00 with partial cloud breaks, creating a viable late-afternoon drying and climbing window.
The rock does not absorb water so only surface moisture matters, allowing faster recovery after rain.
The roadside position in the Llanberis Pass funnels wind across the boulders, accelerating surface drying.
Recommendations
3
- Visit from mid-afternoon onward (after 15:00) when humidity drops and any cloud breaks allow the SW/W-facing rock to catch sun and dry further.
- Physically touch the rock surfaces before committing — check slab faces, low-angle landings, and recessed holds for residual dampness.
- Prioritise steeper and overhanging problems (e.g. Jerry's Roof) which will have stayed drier; avoid slabs and friction-dependent lines if any dampness is detected.
Do Not Climb
92%
11 days ago
Today is a washout at Cromlech Boulders — 10mm of rain spread throughout the day with near-constant 94–99% humidity means the rock will be thoroughly wet and dangerously slippery. The coming days show an unsettled pattern with further rain forecast, offering limited reliable dry windows.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside in the Llanberis Pass and catch cloud and mist funnelling through the valley, which can keep surfaces damp even when rain stops.
- The SW/W aspect means the prevailing SW winds today and in coming days will drive moisture directly onto the rock faces.
- Jerry's Roof and other overhanging problems may appear dry underneath but surrounding landings and slab approaches will be slick and hazardous.
- Cromlech Boulders get extremely crowded on dry summer weekends — if a brief dry window appears mid-week, conditions and crowds may both be more manageable.
Warnings
2
- Wet rhyolite is extremely slippery — friction loss on the Cromlech Boulders makes even easy problems dangerous in these conditions.
- The Llanberis Pass can see rapid weather changes; do not assume a brief dry spell means the rock is climbable.
Reasoning
The rock is currently wet from persistent rain throughout today (10mm total, with showers from 06:00 through to evening) and humidity has been at or above 93% for most of the day.
Despite strong winds (20–28 km/h), the SW/W aspect is directly exposed to the moisture-laden prevailing wind, and near-saturation humidity (87–98%) prevents effective evaporative drying.
Rhyolite is non-porous and structurally unaffected by moisture, so there is no hold breakage or rock damage concern.
Summer conditions should favour rapid drying in principle, but the current unsettled Atlantic pattern with low temperatures (14–18°C) and high humidity is suppressing drying rates significantly.
Contributing Factors
5
10mm of rain spread across most of the day with showers continuing into the evening leaves all boulder surfaces thoroughly wet.
Humidity has been 93–99% throughout the day, preventing any meaningful surface drying between showers.
The SW/W aspect is fully exposed to the moisture-laden southerly and south-westerly airflow driving today's weather system.
Winds of 20–28 km/h would normally aid drying, but with saturated air they are instead depositing moisture onto the rock surfaces.
Rhyolite does not absorb water, so once rain stops and humidity drops the rock will dry relatively quickly — but those conditions are not present today.
Recommendations
3
- Do not climb today — the rock is wet and slippery throughout.
- Thursday 7th August offers the best window this week; arrive after mid-morning to allow overnight dew to clear and visually check for residual seepage.
- If visiting this week, bring alternative plans such as indoor climbing at Indy in Caernarfon or The Beacon in Llanberis.
Marginal — Assess Conditions
62%
12 days ago
After a light shower overnight, today offers a dry and warm window roughly 09:00–16:00 with clearing skies and dropping humidity, which should allow the exposed rhyolite boulders to dry quickly. However, rain is forecast to return from late afternoon onwards, and the coming week looks very wet, so this midday window may be the last good opportunity for several days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside in the Llanberis Pass with a SW/W aspect and good exposure, meaning even light morning dew or overnight drizzle can dry within a couple of hours once the sun and wind pick up.
- Jerry's Roof and other overhung problems may hold seepage or condensation on their undersides longer than vertical faces, so inspect holds carefully even when the rest of the boulder feels dry.
- The pass can funnel wind effectively from SW/W directions, which aids drying today but also channels incoming Atlantic fronts — conditions can change rapidly.
- Weekend and bank holiday crowds can be intense at this venue; arriving early to secure problems during the dry window is advisable.
Warnings
2
- Rain returns from late afternoon today — do not rely on evening conditions remaining dry.
- The coming 5-day forecast shows 39mm of rain; conditions will be unsafe for much of the week ahead.
Reasoning
Only 0.2mm fell overnight (01:00) with a trace at 04:00, and the preceding days saw scattered light rain (0.1–0.6mm); surface moisture on the exposed rhyolite should be minimal by mid-morning.
The SW/W aspect will receive direct solar radiation from late morning, and with moderate SE winds (15–24 km/h) and humidity dropping to 45–50% by midday, surface drying should be rapid — likely complete by 09:00–10:00.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no hold-breakage risk from the recent light precipitation.
Peak summer conditions with long daylight hours and warm temperatures favour quick drying, though the current unsettled Atlantic pattern with high humidity and frequent fronts is typical for a Welsh August.
Contributing Factors
6
A trace of rain fell around 01:00 and 04:00, leaving some residual surface moisture that needs to evaporate before climbing.
From approximately 09:00 to 16:00 the forecast shows zero precipitation, clearing cloud, temps up to 25°C, and humidity dropping to 45%, creating excellent drying conditions.
Rain is forecast from 17:00 onwards (0.6mm+), ending the climbing window and wetting the rock again ahead of a very wet week.
The exposed position with 15–24 km/h SE winds through the pass will accelerate surface drying on the non-porous rhyolite.
The last week has seen repeated light rain events (5.4mm total) and elevated humidity (78% average), meaning the surrounding ground and sheltered recesses may harbour residual dampness.
Nearly 40mm of rain is forecast over the next 5 days, making conditions increasingly unsuitable from tomorrow onwards.
Recommendations
3
- Aim to climb between approximately 10:00 and 16:00 today for the best friction — check holds by hand before committing, especially on slabby or friction-dependent problems.
- Pack up before 17:00 as rain is forecast to return; the rock will become slippery quickly once wet.
- Consider postponing any visits planned for tomorrow through mid-week, as heavy and persistent rain is forecast with no meaningful dry windows.
Climbing Outlook