Condition Analysis
AI-powered assessment using site data and 14-day weather history
The RAC Boulders have had three excellent dry days (Aug 11–13) with warm temperatures up to 29°C, which should have thoroughly dried the rock surface after the rain on Aug 9–10. However, today (Aug 14) shows 0.1mm precipitation and high humidity (89%), introducing slight uncertainty about current surface conditions.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit right beside the A5 road near Llynnau Mymbyr, making them easy to visually inspect on arrival — a quick touch test on multiple faces will confirm whether residual dampness lingers.
- The west-facing aspect means the boulders receive afternoon and evening sun; morning sessions may encounter dew or residual overnight moisture, especially given today's 89% humidity.
- Some lower boulders near the lakeside can retain ground-level moisture and seepage from the grassy surrounds, particularly after the wetter spell earlier in August.
- Being predominantly easy-to-moderate problems (V0–V4) with flat grassy landings, the consequence of a minor friction loss is lower than at steeper venues, but caution is still warranted on any slabby or friction-dependent lines.
Warnings
1
- Today's 89% humidity may cause condensation on rock surfaces, especially on shaded faces — test friction carefully before committing to any slab or friction-dependent problems.
Reasoning
Three fully dry, warm days (Aug 11–13, peaking at 29.4°C) following minor drizzle on Aug 9–10 should have fully evaporated surface moisture on non-porous rhyolite, though today's 0.1mm and 89% humidity may have reintroduced a light film of moisture.
The west-facing aspect and partial wind exposure allow reasonable afternoon drying; the strong dry spell of Aug 11–13 with SW winds around 15 km/h provided excellent drying conditions, but today's elevated humidity limits further evaporation.
Rhyolite is non-porous and does not suffer structural weakening when wet — there is no hold-breakage risk from recent moisture.
Mid-August in Snowdonia is peak summer with long daylight hours and generally warm temperatures, though the Atlantic influence means humidity can spike quickly and rain returns frequently.
Contributing Factors
5
Aug 11–13 brought three consecutive dry days with temperatures reaching 29.4°C, providing excellent drying conditions for non-porous rhyolite surfaces.
Today's 89% humidity and 0.1mm precipitation may leave a thin film of moisture or condensation on rock surfaces, particularly in the morning.
Rhyolite does not absorb water so dries quickly once rain stops — only surface moisture affects friction, and no structural risk exists.
The west-facing boulders will catch afternoon and evening sun today, which should help burn off any residual surface dampness by mid-afternoon.
A significant wet spell (11.6mm + 3.1mm) is forecast for Aug 18–19, which will end the current broadly dry window.
Recommendations
3
- Visit in the afternoon when the west-facing aspect has had time to receive direct sun and burn off any morning dew or condensation from today's high humidity.
- Perform a hands-on touch test on multiple boulder faces before committing — if rock feels greasy or damp, wait or stick to the driest, most sun-exposed problems.
- Plan any climbing for Aug 15–17 to take advantage of the dry forecast window before the significant rain arrives on Aug 18.
Previous Analyses
Likely Safe to Climb
88%
2 days ago
The RAC Boulders are in excellent condition today following three consecutive dry days, warm temperatures, and moderate winds that have thoroughly dried the non-porous rhyolite surfaces. The last significant rain (0.3mm on Aug 10) was trivial, and the last meaningful rainfall (9.9mm on Aug 5) was over a week ago, giving ample drying time.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit close to Llynnau Mymbyr and the lakeside setting can produce localised dew and humidity, especially in the evening — today's humidity rises sharply after 19:00 so afternoon sessions are preferable.
- West-facing aspect means the boulders receive direct sun from early afternoon onwards, which is ideal for today's clear conditions but means morning sessions may feel cooler and slightly damper.
- Roadside location and flat grassy landings can hold moisture after prolonged wet spells — check landing zones for soft or muddy ground near the lake edge.
- Being a popular beginner venue in peak summer, expect company; polish on the easier problems (V0–V2) can reduce friction even when dry.
Reasoning
Three fully dry days with warm temperatures (up to 29°C on Aug 12) and moderate SW winds have ensured complete surface drying of the non-porous rhyolite; today's low daytime humidity (50–60%) confirms dry conditions.
The last trace precipitation (0.1mm on Aug 10) was negligible and three days ago; the west aspect and partial wind exposure with 15–20 km/h winds have provided excellent drying conditions.
Rhyolite is non-porous and does not suffer structural weakening from moisture, so there is no hold breakage risk.
Mid-summer conditions with long daylight hours and warm temperatures are optimal for climbing; the recent dry spell is a welcome window amid an otherwise unsettled August.
Contributing Factors
6
No measurable rain since Aug 10 (0.1mm trace), with the last significant rainfall on Aug 5, providing over a week of effective drying.
Temperatures reached 29°C yesterday and 26°C today with clear skies, accelerating surface evaporation on the west-facing boulders.
Daytime humidity of 50–60% today is well below the levels that would cause condensation or impede drying on rock surfaces.
Consistent 12–17 km/h winds from the SW provide adequate airflow across the partially exposed boulders to keep surfaces dry.
Humidity rises sharply to 90–96% after 19:00 tonight, which could cause condensation on rock surfaces and reduce friction in the evening.
Light rain (0.9mm) is forecast for Aug 14, marking the end of the current dry window.
Recommendations
3
- Climb this afternoon for the best conditions — the west-facing boulders will be in direct sun and humidity is at its lowest between 11:00 and 16:00.
- Avoid evening sessions after 19:00 as humidity rises steeply and condensation may form on rock surfaces, reducing friction.
- Enjoy the window today as unsettled weather returns from tomorrow with light rain forecast through mid-week.
Likely Safe to Climb
92%
3 days ago
RAC Boulders are in excellent condition today — the rock has had two full dry days following only trace precipitation, with warm temperatures (up to 29°C) and low humidity driving thorough surface drying. This is a superb day for bouldering, though conditions deteriorate from Thursday onwards with rain returning.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside near Llynnau Mymbyr and some lower faces close to the lake can retain splash moisture or higher local humidity in calm conditions, though today's warmth and breeze should negate this.
- West-facing aspect means the boulders are in shade during the morning but receive full afternoon and evening sun — ideal for today's forecast of clear skies from midday.
- Flat grassy landings can become slippery and boggy after wet spells; the recent dry spell means landings should be in good shape today.
- As a popular beginner venue, the boulders see heavy traffic and polish on popular lines — friction is excellent on dry rhyolite but polished holds lose grip faster when even slightly damp.
Reasoning
The last meaningful rain was 9.9mm on August 5th, seven days ago, with only trace amounts (0.1–0.3mm) since; the rock surface will be completely dry.
Two consecutive dry days with today reaching 29°C and humidity dropping to 44% provide more than sufficient drying for non-porous rhyolite, even accounting for the west-facing aspect receiving only afternoon sun.
Rhyolite is non-porous and does not suffer structural weakening from moisture; there is no hold breakage or surface damage risk.
Mid-August in Snowdonia offers long daylight hours and warm temperatures; today is an unusually warm and dry day, ideal for friction-dependent bouldering.
Contributing Factors
5
No significant rain for seven days and only 0.4mm total in the last week ensures thoroughly dry rock surfaces.
Today's 29°C peak and 44% afternoon humidity are exceptional drying conditions for Snowdonia, maximising friction on the rhyolite.
Clear skies from midday mean the west-facing boulders will bake in direct sun all afternoon and evening, keeping surfaces warm and dry.
A light SW breeze of 10–14 km/h assists surface drying without being strong enough to affect balance on the boulders.
From August 14th onwards, increasing precipitation is forecast (up to 13mm on the 17th), so today and tomorrow represent the best window.
Recommendations
3
- Make the most of today and tomorrow — these are the best conditions this week, with rain returning from Thursday.
- Afternoon and evening sessions will benefit from direct sun on the west-facing rock, offering peak friction from around 14:00 onwards.
- Check sheltered or north-facing faces of individual boulders for any residual dampness before committing, though all surfaces should be dry in today's warmth.
Marginal — Assess Conditions
72%
5 days ago
The last significant rain was 16.2mm on August 4th and 9.9mm on August 5th, followed by two full dry days (6th–7th), then trace amounts on the 9th and overnight today. Rhyolite dries quickly and surface conditions should be adequate by this afternoon, but residual dampness in sheltered spots and high recent humidity 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 near Llynnau Mymbyr and the lakeside setting can produce localised morning mist and dew, especially after cold clear nights — check north-facing and shaded surfaces carefully.
- Some of the lower boulders closest to the lake edge may retain seepage or ground moisture longer than those set back on higher ground.
- The west-facing aspect means direct sun only arrives in the afternoon; morning sessions may encounter dew or residual dampness that hasn't yet burned off.
- Flat grassy landings can become saturated after prolonged wet spells — check pad placement areas for boggy ground, particularly after the 26mm of rain in the past week.
Warnings
2
- Rhyolite becomes very slippery when wet — even a thin film of moisture from dew or condensation can drastically reduce friction on slab and friction-dependent problems.
- Ground around the boulders may be boggy after recent rain; ensure crash pads are placed on stable, non-slippery ground.
Reasoning
The last heavy rain (16.2mm + 9.9mm) fell on Aug 4–5, giving four mostly dry days for rhyolite surfaces to shed moisture, though trace precipitation on Aug 9 (0.3mm) and overnight (0.1mm) may have left minor surface dampness.
Partial wind exposure and westerly aspect provide reasonable afternoon drying, and the two dry days of Aug 6–7 with ~18–20 km/h winds should have cleared the bulk of the Aug 4–5 rainfall from these non-porous surfaces.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no risk of hold breakage from moisture.
Mid-summer conditions are generally favourable with long daylight hours, though Snowdonia's maritime climate means humidity has been persistently elevated (79% average over the past week), slowing surface drying.
Contributing Factors
6
26.5mm fell in the past 7 days, including a significant 26.1mm across Aug 4–5, which saturated the ground and surrounding vegetation.
Aug 6–8 were fully dry with moderate winds, giving non-porous rhyolite ample time to shed surface water from the Aug 4–5 event.
0.3mm on Aug 9 and 0.1mm overnight mean surfaces may not be perfectly dry right now, though amounts are negligible.
Average humidity of 79% over the past week and 90%+ overnight slows evaporation and promotes condensation on rock surfaces.
Humidity drops to 56–61% this afternoon with clearing skies and light winds, providing a good drying window especially on the west-facing surfaces catching sun.
Aug 11–13 forecast as completely dry with temperatures rising to 23–33°C and dropping humidity, promising excellent conditions in the coming days.
Recommendations
3
- Wait until mid-afternoon today (after 14:00) when the west-facing boulders will have had direct sun and humidity will be at its lowest, and perform a hands-on friction test before committing to problems.
- Prioritise the higher, more exposed boulders set back from the lake which will have dried fastest; avoid any surfaces that feel greasy or show damp patches.
- Tomorrow (Aug 11) and the days following look significantly better — if conditions feel marginal today, returning tomorrow afternoon would be a much more confident session.
Marginal — Assess Conditions
72%
5 days ago
The RAC Boulders received significant rain on Aug 4–5 (26mm total) but have had three full dry days since, with today showing only a trace (0.1mm). As non-porous rhyolite, surfaces should be largely dry, but elevated humidity (mid-70s%) and the recent wet spell warrant a visual check on arrival, particularly for any seepage or lingering dampness in sheltered spots.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit close to Llynnau Mymbyr at 200m altitude, and lake-proximity can maintain local humidity and dew, especially on calm mornings.
- West-facing aspect means the boulders only receive direct sun from mid-afternoon onward — shaded faces and north-facing sides of boulders may retain surface moisture longer.
- Roadside location with partial wind exposure provides reasonable airflow for drying, but some boulders tucked closer to the hillside or trees may be more sheltered.
- The flat grassy landings can remain boggy after prolonged wet spells, which may contribute to splash dampness on lower boulder faces.
Warnings
1
- Grassy landings may still be soft and boggy from recent heavy rain — check pad placements carefully for stability.
Reasoning
Three dry days following the heavy Aug 4–5 rain (26mm) should have cleared surface moisture from rhyolite, but today's trace precipitation and 79% humidity mean conditions are not guaranteed bone-dry.
Partial wind exposure and SW winds around 20–23 km/h have aided drying, though the west aspect limits direct sun to afternoon hours, slowing evaporation on shaded faces.
Rhyolite is non-porous and does not absorb water, so there is no structural weakening or hold breakage risk — the concern is purely surface friction.
Mid-summer conditions with temperatures around 16–20°C and daylight hours are favourable, though the recent spell of unsettled Atlantic weather has kept humidity persistently elevated.
Contributing Factors
7
26mm fell over two days, the heaviest event in the past month, saturating the ground and boulders.
Aug 6–8 were completely dry with moderate winds, providing good surface drying time for non-porous rhyolite.
0.1mm today is negligible but indicates unsettled air and possible light drizzle that could dampen surfaces.
Humidity has averaged 77% over the past week, slowing evaporation and increasing the chance of condensation or dew on the rock.
Winds of 17–23 km/h over recent days have aided surface drying despite the humidity.
Afternoon sun helps dry the main faces but shaded or north-facing sides of boulders may retain dampness longer.
After a trace of rain tomorrow (0.3mm), conditions look dry and warm from Aug 11 onward with temperatures reaching 25–26°C.
Recommendations
3
- Visit in the afternoon when the west-facing boulders have had maximum sun exposure, and test friction carefully on your first few problems.
- Check lower sections and north-facing boulder surfaces for residual dampness or seepage before committing to harder problems.
- If conditions are borderline today, consider waiting until Aug 11 when warmer, drier weather is forecast to arrive.
Marginal — Assess Conditions
72%
6 days ago
Three dry days with moderate wind following a significant wet spell (26mm in a week including 16mm on Aug 4th) should have allowed the non-porous rhyolite surfaces to dry, but elevated humidity (70–77%) and the west-facing aspect receiving limited direct sun may mean some sheltered surfaces retain dampness. A visual check on arrival is recommended.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit near Llynnau Mymbyr at 200m; proximity to the lakes can elevate local humidity and produce morning mist that re-wets surfaces even after dry spells.
- West-facing aspect means the boulders only receive afternoon and evening sun, so north-facing sides and undercut features may stay damp longer after rain.
- Roadside location with flat grassy landings can mean wet grass underfoot even when rock is dry — pad placement and spotter footing deserve attention.
- Being between the Llanberis Pass and Capel Curig, the site funnels prevailing SW winds which aids drying but also channels incoming Atlantic weather rapidly.
Warnings
1
- Rhyolite becomes very slippery when wet — if any surface dampness is found, do not climb on those faces as friction loss on bouldering problems poses a serious fall risk.
Reasoning
The heavy rain on Aug 4–5 (26mm combined) was followed by three completely dry days with moderate SW/W winds, which should have cleared surface moisture from the non-porous rhyolite, though ambient humidity around 70–77% may keep sheltered faces slightly damp.
Three dry days with 17–20 km/h winds from the SW/W directly hitting the west-facing boulders provides reasonable drying, but the partial wind exposure and moderate temperatures (~17–19°C) slow evaporation compared to ideal conditions.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no risk of hold breakage from the recent rainfall.
Mid-summer conditions with long daylight hours and reasonable temperatures favour drying, though the recent spell of cooler, humid weather (15–17°C averages, 76% humidity) is below seasonal norms for August.
Contributing Factors
6
26mm fell across Aug 4–5, with 16.2mm on Aug 4th alone representing the heaviest single-day rain in the past month.
No precipitation since Aug 5th, giving non-porous rhyolite ample time for surface water to evaporate under moderate wind.
Winds of 17–20 km/h from W/SW directions directly strike the west-facing boulders, promoting effective surface drying.
Humidity has remained around 70–77% over the past three days, slowing evaporation and potentially allowing condensation on cooler rock surfaces.
Proximity to Llynnau Mymbyr can produce localised mist and elevated humidity that may re-dampen boulder surfaces, particularly in the mornings.
2mm of rain is forecast for Aug 9th, which will re-wet surfaces and reset drying time.
Recommendations
3
- Visit in the afternoon or evening to maximise the benefit of direct sun on the west-facing rock and allow any morning dampness to clear.
- Physically touch and test friction on multiple surfaces before committing to problems — check sheltered undersides and north-facing faces in particular.
- Be aware that rain is forecast for tomorrow (Aug 9th); today offers the best window before conditions deteriorate again.
Marginal — Assess Conditions
72%
7 days ago
The RAC Boulders received significant rain on Aug 4–5 (26.1mm combined) and have had only two full dry days since. Being non-porous rhyolite, surface moisture should evaporate relatively quickly, but with elevated humidity (76%) and moderate temperatures, some sheltered faces and seepage zones may still be damp — a visual check on arrival is essential.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside near Llynnau Mymbyr at 200m, where lake-effect moisture can keep local humidity higher than valley-floor readings suggest, slowing surface drying.
- West-facing aspects only receive direct sun from early-to-mid afternoon onward, meaning morning sessions may encounter residual overnight condensation, especially in summer's humid spells.
- Several problems have mossy or lichen-covered landings and lower sections that hold moisture longer; the flat grassy ground can remain boggy after wet spells, affecting approach and landing zones.
- As a beginner-friendly roadside venue, the boulders see high traffic — friction pads may be polished on popular V0–V2 lines, reducing grip further if any surface dampness remains.
Warnings
2
- Rhyolite becomes very slippery when damp — friction loss on wet surfaces is a real fall hazard, especially on the many slab and friction problems at this venue.
- Grassy landings may be boggy after the recent wet spell; check pad placement carefully to avoid slipping on wet grass.
Reasoning
After 26.1mm of rain across Aug 4–5, only two dry days have elapsed with moderate humidity (~74–76%), meaning while the non-porous rhyolite surfaces should be largely dry, sheltered overhangs, cracks, and north-facing sides of boulders may retain surface moisture or condensation.
The west aspect receives afternoon sun only, and moderate SW winds (17–25 km/h) provide reasonable airflow, but the partial shelter and 200m altitude limit drying efficiency — two days is adequate for exposed faces but marginal for recessed or shaded features.
Rhyolite is non-porous and extremely hard; there is no risk of structural weakening or hold breakage from this rainfall.
Mid-summer conditions are broadly favourable with long daylight hours aiding drying, though the recent shift to cooler, more humid Atlantic weather (15–17°C, humidity 74–91%) is typical of a Welsh August pattern change.
Contributing Factors
6
26.1mm fell across Aug 4–5 with only two full dry days since, which is marginal for complete surface drying of all boulder faces at this partially sheltered site.
Rhyolite does not absorb water, so drying is purely a surface process and proceeds quickly once rain stops.
Humidity has averaged 76% over the last week and remains at 74–76% today, slowing evaporation and raising the chance of overnight condensation.
Partial wind exposure with 17–19 km/h SW winds aids surface drying across exposed faces.
West-facing boulders catch afternoon and evening sun, which helps dry surfaces from midday onward.
The next two days forecast 0mm precipitation with rising temperatures (20–22°C) and dropping humidity (69–70%), which will significantly aid drying.
Recommendations
3
- Visit in the afternoon when west-facing surfaces have had several hours of direct sun; avoid early morning sessions when condensation is likely.
- Physically touch rock surfaces before committing — check sheltered undersides, cracks, and north-facing aspects of individual boulders for residual dampness.
- Consider waiting until Aug 8 or 9 for more confident dry conditions, as the improving forecast will provide substantially better friction.
Do Not Climb
45%
9 days ago
Heavy rain today (8.4mm, mostly falling between 11:00–15:00) follows a very wet spell of 36mm over the past week, leaving the boulders wet and conditions unsuitable for climbing. Although a brief clearing window appears late afternoon, the rock will still be damp from showers just hours earlier and residual moisture from the prolonged wet period.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The RAC Boulders sit at roadside level near Llynnau Mymbyr and can collect runoff and splash from passing traffic in wet conditions, adding to surface moisture.
- West-facing aspect means the boulders catch afternoon and evening sun — the clearing forecast from 16:00 onwards will help surface drying, but only a few hours of sun after heavy midday rain is insufficient for reliable friction.
- Being low-lying boulders near a lake, overnight humidity and morning dew can keep surfaces damp even after dry days, particularly at 80%+ humidity levels.
- Flat grassy landings can become waterlogged after prolonged rain, making spotting and landing zones slippery and potentially unsafe.
Warnings
2
- Wet rhyolite is extremely slippery — friction loss on damp surfaces creates serious fall risk, especially on the slab and friction-dependent problems common at this venue.
- Do not be deceived by a late-afternoon clearing; surface moisture from midday showers may persist in textured holds and on north-facing facets of individual boulders.
Reasoning
The boulders are actively receiving rain today with 8.4mm forecast, on top of 26mm in the preceding three days (Aug 4–5), so surfaces will be thoroughly wet.
Although rain stops around 15:00–16:00 and a clearing window with moderate westerly wind follows, only 2–3 hours of drying after heavy showers on non-porous but textured rhyolite is marginal at best.
Rhyolite is non-porous and does not suffer structural damage from moisture; the risk is entirely friction-based — wet rhyolite is notoriously slippery.
Mid-summer provides long daylight hours and reasonable temperatures, but the current unsettled spell with SW airflow is bringing Atlantic moisture typical of a Welsh summer breakdown.
Contributing Factors
6
Approximately 8.4mm of rain is falling today, with the heaviest showers between 11:00 and 15:00, keeping the rock saturated.
Over 36mm of rain in the past 7 days means the surrounding ground is saturated and general moisture levels are elevated.
Humidity has averaged 77% over the past week and remains 80% today, significantly slowing surface evaporation.
Rain stops by 16:00 with cloud breaking and humidity dropping to 64%, offering a narrow window where surface drying can begin.
The west-facing boulders will receive direct sun during the late-afternoon clearing, aiding surface drying from around 16:00–19:00.
Partial wind exposure with 11–15 km/h westerly winds this afternoon will assist surface evaporation once rain ceases.
Recommendations
3
- Wait until tomorrow (Aug 7) at the earliest, and ideally Aug 8 or 9 when a drier, warmer spell is forecast to allow proper drying.
- If visiting late today out of curiosity, physically test friction on easy low problems before committing — wet rhyolite offers dramatically reduced grip.
- Check that grassy landings are not waterlogged before placing pads; saturated ground after 36mm in a week may make landings unsafe.
Do Not Climb
92%
11 days ago
Heavy rain today (12.7mm) with intermittent showers throughout the day and near-saturated humidity means the boulders will be thoroughly wet. Even the non-porous rhyolite will be dangerously slippery in these conditions, with no viable dry window today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The RAC Boulders sit in the Mymbyr valley corridor which funnels SW weather systems, meaning they catch the full brunt of frontal rain arriving from the Atlantic.
- West-facing aspect means the boulders receive no morning sun to aid early drying; any drying relies on afternoon/evening sun which is absent under today's 100% cloud cover.
- Roadside boulders with flat grassy landings can become slippery underfoot as well as on the rock, increasing the risk of pad and spotter slips on wet grass.
- Being a low-altitude, beginner-friendly venue, it may attract less experienced climbers who are more vulnerable to the friction loss on wet rhyolite — extra caution is warranted.
Warnings
2
- Wet rhyolite loses friction dramatically — do not attempt to climb even if the rock appears only slightly damp.
- Grassy landings around the RAC Boulders will be saturated and slippery, increasing the risk of ankle injuries on dismounts and falls.
Reasoning
The rock is currently saturated from 12.7mm of rain today, with showers continuing throughout the day and humidity consistently above 90%.
No meaningful drying is occurring — continuous showers, 100% cloud cover, and very high humidity (91–99%) negate any benefit from the moderate SW wind.
Rhyolite is non-porous and not at risk of structural damage from moisture, but surface friction is severely compromised when wet.
Summer conditions are generally favourable for recovery, but this is an unsettled spell with further rain forecast over the coming days, preventing a quick return to dry conditions.
Contributing Factors
6
12.7mm of precipitation today with showers spread across most hours makes the rock thoroughly wet.
Humidity between 90–99% all day prevents any evaporative drying of surface moisture.
100% cloud cover throughout the day eliminates solar heating that would otherwise help dry the west-facing rock.
Winds of 15–27 km/h could aid drying on an exposed surface, but are ineffective at the current extreme humidity levels.
Nearly 17mm in the past 7 days and repeated showers since July 25th mean the surrounding ground and vegetation are saturated, contributing to ambient moisture.
Rhyolite does not absorb water, so once surface moisture evaporates the rock will regain full friction without needing extended drying time.
Recommendations
3
- Do not climb today — the boulders are wet and slippery with no dry window available.
- The earliest realistic opportunity is August 7th after a forecast dry day; check conditions on arrival as residual seepage may linger.
- If visiting the area today, consider scoping out problems and cleaning landings in preparation for drier conditions later in the week.
Marginal — Assess Conditions
62%
12 days ago
There is a narrow dry window today roughly from mid-morning through mid-afternoon before rain returns from 17:00 onwards; the light overnight drizzle should dry quickly on non-porous rhyolite in the warm, sunny conditions forecast for late morning. However, the coming week looks persistently wet with rain forecast on most days, so today's window may be the best opportunity for several days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside near Llynnau Mymbyr and can accumulate moisture from lake-effect humidity, especially in calm early mornings — check for condensation on rock surfaces before committing.
- West-facing aspect means direct sun only arrives from late morning/early afternoon, so overnight dampness lingers longer here than at south-facing venues.
- Flat grassy landings can become saturated and slippery after the recent wet spell (9.3mm in 7 days), making pad placement and spotting less reliable.
- Being a beginner-friendly bouldering venue, many problems rely on friction-dependent slab and low-angle moves where even slight residual moisture dramatically increases slip risk.
Warnings
2
- Rain is forecast to return from 17:00 today — do not rely on a late-afternoon or evening session.
- The upcoming week looks persistently wet; plan alternative activities or indoor climbing if visiting Snowdonia in the next 5 days.
Reasoning
Light drizzle overnight (0.3mm total before 05:00) on top of recent intermittent rain means rock surfaces are likely damp this morning, though rhyolite's non-porous nature means moisture is purely surficial.
With clearing skies forecast from 09:00, temperatures rising to 25°C, humidity dropping to 44%, and moderate SE winds (~15 km/h), surface moisture should evaporate within 1–2 hours of sun exposure, giving dry rock by late morning.
Rhyolite does not absorb water so there is no structural weakening or hold breakage risk from the recent wet period.
Mid-summer provides long daylight hours and warm temperatures that aid rapid drying, though Snowdonia's maritime climate means humidity remains elevated and showers are frequent even in August.
Contributing Factors
6
Around 0.3mm of drizzle fell between midnight and 04:00, leaving surfaces damp this morning.
Clear skies forecast from 09:00–16:00 with temperatures reaching 25°C and low humidity (44%) should dry rock surfaces effectively by late morning.
Rain is forecast from 17:00 onwards (1.2mm+ through the evening), closing the climbing window and re-wetting surfaces.
9.3mm over the past 7 days with rain on 5 of those days means the surrounding ground and any seepage areas may still be damp.
Peak temperatures of 25°C with moderate wind and dropping humidity create good evaporative conditions during the dry window.
The forecast shows rain on 4 of the next 5 days totalling nearly 19mm, meaning conditions will deteriorate and not recover soon.
Recommendations
3
- If climbing today, aim for the window between approximately 11:00 and 16:00 when surfaces should be dry and friction at its best — physically touch the rock to check before climbing.
- Avoid any problems that sit in natural drainage lines or have north-facing overhangs that may retain overnight dampness longer.
- Check landing areas carefully as the grassy ground may be soft and slippery after the recent wet spell; position pads with extra care.
Climbing Outlook