Condition Analysis
AI-powered assessment using site data and 14-day weather history
The RAC Boulders are currently wet and conditions are unsuitable for climbing. An extended period of heavy rainfall (over 40mm in the last 7 days, 160mm in the last 28 days), ongoing rain today with 8.7mm forecast, and near-100% humidity throughout mean the rock will be saturated on the surface with no drying opportunity. The forecast shows continuous rain for at least the next 5 days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The RAC Boulders sit in the Mymbyr valley which can funnel moist SW airflow, and the prevailing SW winds of the past weeks will have driven rain directly onto the west-facing rock surfaces.
- Roadside boulders at 200m in this part of Snowdonia are prone to low cloud and persistent drizzle even when precipitation totals appear modest — the 97% humidity today indicates the rock is likely condensation-wet even between showers.
- Some boulders here have mossy bases and lichen on less-trafficked faces which become treacherously slippery when wet, particularly the easier slab problems.
- The flat grassy landings become boggy and soft after prolonged rain, reducing the effectiveness of crash pads and increasing the risk of ankle injuries on awkward landings.
Warnings
2
- Wet rhyolite is extremely slippery — the slab and friction problems that dominate this venue become genuinely dangerous when damp.
- Grassy landings will be waterlogged after weeks of heavy rain, reducing crash pad stability and increasing injury risk from slips.
Reasoning
The rock is currently wet from overnight and morning drizzle, with humidity at 100% preventing any evaporation, and heavier rain (3mm+/hr) forecast from late afternoon onwards.
There has been no meaningful drying window — the last fully dry day was June 14 (0.0mm), but June 15 brought 1mm and today has been persistently damp with 100% humidity, so any brief drying was immediately negated.
Rhyolite is non-porous and not at risk of structural damage from moisture, but surface friction is severely compromised when wet, making the predominantly slab and friction-dependent problems at this venue dangerous.
Early June in Snowdonia is experiencing an unusually wet spell with nearly 160mm over 28 days; the persistent SW flow is a classic pattern for prolonged Snowdonian rain and shows no sign of breaking until at least June 22.
Contributing Factors
6
Over 40mm in the past 7 days and 160mm in 28 days, with significant events on June 11 (27mm), June 8 (20mm), and June 1 (31mm) keeping the environment thoroughly saturated.
8.7mm total forecast today with heavy showers from 15:00–21:00 and 100% humidity through the morning, meaning the rock is wet now and will get wetter.
Humidity has been 80–100% for the past week and is 97% today, completely preventing surface evaporation even during dry spells.
The next 5 days show rain every day totalling 56mm, with no drying window until possibly June 22.
The west-facing boulders are fully exposed to the prevailing SW rain-bearing winds, receiving maximum wetting from the dominant weather pattern.
Partial wind exposure would normally aid drying, but with continuous rain and near-100% humidity the wind is simply driving more moisture onto the rock.
Recommendations
3
- Do not visit for climbing today or in the coming days — the prolonged wet spell makes conditions unsafe on these friction-dependent rhyolite boulders.
- Monitor conditions from June 22 onwards when the forecast shows a potential dry window; the rock could dry within a few hours of sunshine and wind given rhyolite's non-porous nature.
- If in the area, consider visiting indoor walls in Llanberis (Beacon Climbing Centre) or Betws-y-Coed as alternatives during this wet spell.
Previous Analyses
Marginal — Assess Conditions
55%
2 days ago
After a very wet week (37mm in the last 7 days, heavy rain on June 11), two dry days on June 13–14 and a mostly dry today have allowed surface drying on the non-porous rhyolite, but persistent high humidity and overcast skies may leave some surfaces damp; a narrow afternoon window today (roughly 10:00–18:00) offers the best chance before heavy rain arrives tomorrow.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit at roadside near Llynnau Mymbyr and some lower problems close to the lake may retain splashback moisture or be affected by rising damp from the grassy landings after prolonged wet spells.
- The west-facing aspect means the boulders only receive afternoon and evening sun, so morning condensation and overnight dew can linger well into late morning — particularly relevant given today's 100% cloud cover until mid-morning.
- The flat grassy landings that make RAC Boulders so beginner-friendly can become saturated after extended wet periods like the last fortnight, potentially wicking moisture onto the base of problems.
- This venue is very popular with beginners and families; be aware that lower-grade slabs rely heavily on friction and are the most affected by residual surface moisture — test friction carefully before committing.
Warnings
2
- Heavy rain (20mm+) is forecast for tomorrow June 16, making conditions clearly unsuitable from tomorrow through at least June 20.
- High humidity and overcast skies may leave a deceptive film of moisture on slab faces that appears dry but offers reduced friction — test carefully before trusting feet on slabs.
Reasoning
The last significant rain was 27.1mm on June 11, followed by trace precipitation on June 12 (0.2mm) and two fully dry days; surface moisture on the non-porous rhyolite should have largely evaporated, though high ambient humidity (75–81%) may slow the final drying of sheltered faces.
Two full dry days with moderate westerly winds (25–37 km/h on June 12–13) and the west-facing aspect receiving afternoon sun have provided reasonable drying conditions, though the persistent cloud cover and humidity above 75% limit evaporation rates compared to a true sunny spell.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no hold breakage risk from moisture, so the concern is purely friction and safety.
Early June in Snowdonia brings long daylight hours and moderate temperatures favourable for drying, but the current unsettled Atlantic pattern is delivering frequent rain and high humidity that offset the seasonal advantage.
Contributing Factors
6
150mm over the past 28 days including 27mm on June 11 and 20mm on June 8 indicate a prolonged wet period saturating the surrounding ground.
June 13 and 14 were essentially dry with moderate wind, giving the non-porous rhyolite surfaces roughly 48 hours to shed surface moisture.
Humidity has averaged 81% over the past week and today's morning hours show 80–89%, slowing evaporation and potentially leaving a film of moisture on shaded surfaces.
Today's hourly forecast shows no precipitation until 23:00 with humidity dropping to 60–65% between 13:00–17:00, offering a viable climbing window.
20.4mm forecast for June 16 with 97% humidity will thoroughly re-wet all surfaces, closing conditions for days.
The west-facing boulders catch afternoon sun when available, but today's 100% cloud cover negates direct solar drying for most of the day.
Recommendations
3
- If climbing today, target the afternoon window (roughly 12:00–18:00) when humidity is lowest and test friction on a low easy problem before committing to anything committing.
- Avoid the more friction-dependent slabs and prioritise juggy, steeper problems where residual dampness is less of a safety concern.
- Do not plan to climb from tomorrow (June 16) onwards until you see a sustained dry spell — the forecast shows rain every day through June 20.
Marginal — Assess Conditions
60%
3 days ago
After a very wet period (57mm in the last 7 days, 150mm in the last 28 days), the RAC Boulders have had only 2 dry days with light winds today. The rhyolite surfaces may be dry in sun-exposed areas but seepage and residual dampness in sheltered spots are likely given the saturated ground conditions.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit at roadside level near Llynnau Mymbyr, and the surrounding flat grassy ground can become waterlogged after prolonged rain, potentially wicking moisture onto lower boulder surfaces.
- West-facing aspect means the boulders only receive afternoon and evening sun, so north-facing sides and shaded recesses will retain moisture longer — particularly relevant after 150mm in 28 days.
- Being roadside boulders at 200m with partial wind exposure, they benefit from reasonable airflow, which aids surface drying on the rhyolite even when ground saturation is high.
- Some problems on the lower sections of boulders may have damp landings or moss/lichen patches that become slippery after prolonged wet spells — check footholds carefully.
Warnings
2
- The ground around the boulders may be waterlogged after 150mm of rain in 28 days — check landing zones are not boggy before committing to problems.
- Rain is forecast to return from June 16 onwards with significant falls on June 17 (10.7mm); conditions will deteriorate again mid-week.
Reasoning
Two full dry days following 27mm on June 11 and a prolonged wet spell should have allowed exposed rhyolite surfaces to shed most surface water, but ambient humidity remains high (75–78%) and ground saturation is significant.
Today's light northerly wind (11.5 km/h) and the west-facing aspect mean limited direct drying today; yesterday's stronger westerly winds (37 km/h) and dry weather would have aided surface drying considerably on exposed faces.
Rhyolite is non-porous and not at risk of structural damage from moisture; the concern is purely friction loss on any remaining damp patches.
Early June in Snowdonia brings long daylight hours and reasonable temperatures (14–17°C), supporting drying, but this has been an exceptionally wet period even by Welsh standards.
Contributing Factors
7
57mm in the last 7 days and 150mm over 28 days has thoroughly saturated the ground and surrounding environment around the boulders.
June 13 and 14 have been dry, allowing non-porous rhyolite surfaces to begin shedding surface moisture.
Humidity has averaged 81% over the past week and remains at 75–78% today, slowing evaporation and potentially leaving a film of moisture on rock.
Westerly winds of 37 km/h on June 12 would have helped strip surface moisture from the west-facing boulders effectively.
Today's northerly wind at only 11.5 km/h provides limited drying assistance, especially on west-facing surfaces sheltered from a north wind.
The boulders only catch afternoon and evening sun, meaning morning sessions may encounter lingering dampness on shaded faces.
Rain returns as early as tomorrow (0.2mm) with heavier falls of 10.7mm on June 17, limiting the drying window.
Recommendations
3
- Visit in the afternoon or evening when the west-facing boulders have had maximum sun exposure, and test friction on lower-grade problems before committing to anything harder.
- Inspect each boulder carefully for damp patches, seepage streaks, and lichen — particularly on north-facing sides and near ground level where waterlogged grass may wick moisture.
- If planning to climb later this week, aim for June 15 (tomorrow) as the best remaining window before heavier rain arrives on June 17.
Do Not Climb
35%
4 days ago
The RAC Boulders have been subjected to an extremely wet period with 69mm in the last 7 days and 150mm over 28 days, with only one full dry day since the last significant rainfall (27.1mm on June 11). While today is dry, the rock is very likely still damp in sheltered areas and seepage zones, and more rain is forecast from June 16 onwards.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit at roadside level near Llynnau Mymbyr and ground-level moisture from saturated grassy landings can keep the base of problems damp even when the rock face itself appears dry.
- West-facing aspect means the boulders only receive afternoon and evening sun, limiting the drying window — particularly problematic during this cool, humid spell with temperatures well below seasonal norms.
- Some of the boulders have overhanging faces and sheltered undersides that can harbour residual moisture and seepage long after exposed faces have dried.
- The A5 road proximity means easy access for a quick visual check — worth driving past to assess before committing, as conditions can vary boulder to boulder.
Warnings
2
- Rhyolite becomes extremely slippery when wet — even a thin film of moisture can cause unexpected foot slips on slab problems.
- The saturated grassy landings may be slippery and soft; take extra care with pad placement and spotting.
Reasoning
With 27.1mm falling on June 11, only a trace on June 12, and just one dry day (today), surface moisture is very likely still present in sheltered areas despite the non-porous nature of rhyolite.
Today's westerly wind at 24 km/h and dry conditions will help exposed west-facing surfaces, but the cool temperatures (14°C max), high humidity (78%), and limited afternoon-only sun exposure mean drying is slow.
Rhyolite is non-porous and does not suffer structural weakening when wet, so hold breakage is not a concern here.
Early June temperatures are running well below seasonal averages (11.8°C over 7 days vs typical 16–18°C), which significantly slows evaporation and extends drying times.
Contributing Factors
7
69mm in the last 7 days including 27.1mm on June 11 and 20.2mm on June 8 has kept the site persistently wet.
Just one full dry day since the last significant rain is insufficient for reliable drying of all boulder surfaces, especially sheltered faces.
Average humidity of 84% over the past week severely impedes evaporation and surface drying.
Temperatures averaging 11.8°C are well below early-June norms, further slowing the drying process.
Westerly wind at 24 km/h directly hitting the west-facing boulders will assist surface drying on exposed faces.
Rhyolite does not absorb water, so surface moisture will evaporate faster than on porous rock types once conditions allow.
Significant rainfall is forecast from June 16 (9mm) through June 17 (25.7mm), limiting the available dry window.
Recommendations
3
- Wait until tomorrow (June 14) at the earliest, and visually inspect each boulder before climbing — look for damp patches, dark streaks, and test friction with an open palm.
- If visiting June 14–15, prioritise exposed, sun-catching faces and avoid shaded or north-facing sides of boulders where moisture will linger longest.
- Avoid climbing from June 16 onwards as heavy rain returns; the best window this week is the afternoon of June 15 if conditions have dried sufficiently.
Do Not Climb
40%
5 days ago
The RAC Boulders have been subjected to a prolonged wet spell with 74mm in the last 7 days alone, culminating in 27mm yesterday and only a trace of rain today. Despite rhyolite being non-porous, the boulders will still have significant surface moisture, seepage, and saturated ground surroundings — conditions are not yet suitable for climbing.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside at 200m in the Nant Gwryd valley, which funnels moisture-laden SW winds directly onto the rock, meaning the prevailing rain direction during this wet spell has been hitting the boulders head-on.
- West-facing aspect means afternoon/evening sun only, and with recent cloud cover and high humidity (85%+ average), effective solar drying has been minimal over the past week.
- Flat grassy landings around the boulders will be thoroughly waterlogged after 150mm in 28 days, creating splash-up moisture and persistently damp conditions at the base of problems.
- Some boulders have overhanging faces and roofs that may have stayed drier, but lower slabs and vertical faces will retain surface water and lichen moisture in this prolonged wet period.
Warnings
2
- Rhyolite becomes extremely slippery when wet — do not attempt friction-dependent slab problems until surfaces are fully dry.
- Ground saturation after 150mm in 28 days means landings may be soft and unstable; assess pad placement carefully.
Reasoning
With 27mm falling yesterday, 4.8mm on June 10, and only 0.3mm today, the rock surfaces are almost certainly still damp or wet, and high ambient humidity (81%) is impeding evaporation.
Today's strong westerly wind (35.6 km/h) hitting the west-facing boulders directly will help surface drying, but with zero consecutive fully dry days and persistent high humidity, one windy afternoon is insufficient to clear moisture from all surfaces and seepage lines.
Rhyolite is non-porous so there is no structural risk from moisture absorption; the concern is entirely friction loss on wet or damp surfaces.
Early June in Snowdonia often brings prolonged Atlantic weather systems, and this spell is a classic example; temperatures are below seasonal average, further slowing evaporation.
Contributing Factors
6
74mm in the last 7 days including 27mm yesterday means rock surfaces, cracks, and surrounding ground are thoroughly saturated.
Today still recorded 0.3mm of precipitation, so there has been no complete dry day to begin meaningful drying.
Average humidity of 85% over the past week with 81% today severely limits evaporative drying of surface moisture.
35.6 km/h westerly wind hitting the W-facing boulders directly provides some useful surface drying effect.
Three consecutive dry days forecast from June 13–15 with improving temperatures should progressively dry the rock.
Rhyolite does not absorb water, so drying is limited to surface evaporation which can occur relatively quickly once conditions allow.
Recommendations
3
- Wait at least until June 14 to allow two full dry days with wind exposure before attempting any climbing here.
- If visiting on June 14 or 15, prioritise west-facing overhanging problems that are most exposed to wind and sun; avoid slabs and lower-angle faces which retain moisture longest.
- Check the grassy landings carefully — they will be waterlogged and potentially slippery, so bring extra pads and consider footwear for the approach.
Do Not Climb
95%
6 days ago
The RAC Boulders are currently soaked after 31mm of rain today on top of over 80mm in the past week. With 94% humidity and continuous cloud cover, the rock will remain wet and dangerously slippery for the rest of today and into tomorrow.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit roadside at 200m in the Mymbyr valley, which funnels moist SW airflow and can stay damp longer than the weather station data alone suggests.
- West-facing aspect means the boulders only receive afternoon and evening sun — with 100% cloud cover forecast for the coming days, this advantage is largely negated.
- Flat grassy landings become saturated and slippery after prolonged rain, increasing the risk of ankle injuries even on the easy problems that define this venue.
- Some of the lower boulders near the lake edge can experience ground-level moisture wicking and seepage that persists well after the rock faces themselves have dried.
Warnings
2
- Wet rhyolite is extremely slippery — do not attempt to climb even 'easy' problems while the rock is damp, as falls from even low height onto saturated grassy landings risk injury.
- The prolonged wet spell means grass landings are waterlogged; consider bringing extra crash pads if climbing later this week.
Reasoning
The rock is thoroughly wet after 31mm of heavy rain today, following an extremely wet period of 80mm in the past 7 days and nearly 154mm over 28 days.
Despite rhyolite's non-porous nature, surface drying is severely hampered by persistent 94–97% humidity, 100% cloud cover, and continued light rain forecast for the next two days.
Rhyolite does not suffer structural weakening when wet, so hold breakage is not a concern; the risk is purely friction loss on wet surfaces.
Early June in Snowdonia is experiencing an unusually prolonged wet spell; temperatures are below seasonal average, slowing evaporation and keeping humidity elevated.
Contributing Factors
6
31mm of rain fell today, most of it between 06:00 and 16:00, thoroughly wetting all boulder surfaces.
Over 80mm in the last 7 days means the surrounding ground and any crevices are saturated, contributing to persistent surface moisture.
Humidity has been 94–97% all day with 100% cloud cover, preventing any meaningful evaporation or drying.
SW winds of 25–30 km/h provide some airflow but are insufficient to dry rock when humidity exceeds 90%.
Rhyolite does not absorb water, so once conditions improve the surface will dry relatively quickly — hours rather than days.
Light rain (1.5mm and 1.8mm) is forecast for June 12 and 13, delaying any meaningful drying window until June 14.
Recommendations
3
- Do not climb today — the boulders are actively wet and friction on rhyolite is very poor in these conditions.
- The first realistic window is June 14, which shows 0mm rain, lower humidity (80%), and warming temperatures — but arrive in the afternoon to allow morning dew to burn off.
- Check conditions in person on arrival even on dry-forecast days, as valley-floor boulders near Llynnau Mymbyr can retain surface moisture from lake proximity and ground saturation.
Do Not Climb
92%
8 days ago
RAC Boulders are currently saturated after a prolonged wet spell delivering over 75mm in the last 7 days, with rain today and more forecast through the week. Even though rhyolite dries relatively quickly, the persistent rainfall and high humidity (86% average) mean surfaces will remain wet and slippery with no meaningful drying window today or in the coming days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- RAC Boulders sit at roadside level near Llynnau Mymbyr and can accumulate ground-level moisture and splash from passing traffic, adding to surface dampness during prolonged wet spells.
- The west-facing aspect means the boulders only receive afternoon and evening sun, which is insufficient to drive rapid drying during overcast, humid conditions like this current spell.
- The flat grassy landings can become waterlogged and slippery after sustained rain, increasing the risk of injury on even low-grade problems.
- Being a beginner-friendly venue, extra caution is warranted as less experienced climbers may not recognise how dramatically rhyolite friction drops when wet.
Warnings
3
- Rhyolite becomes extremely slippery when wet — the loss of friction is dramatic and falls are likely even on easy problems.
- Grassy landings will be waterlogged and slippery after this sustained rain, increasing injury risk from even short falls.
- Do not be tempted by brief dry spells between showers today — the rock will not have time to dry and surface moisture may be hard to see.
Reasoning
With 75mm of rain in the past 7 days, rain earlier today, and a further shower forecast at 16:00, the rock surfaces are currently wet and will not achieve a dry state today.
Despite partial wind exposure and SW winds around 25–30 km/h, the persistent high humidity (80%+) and repeated rainfall events prevent any meaningful drying between showers.
Rhyolite is non-porous and not at risk of structural damage from moisture, so hold breakage is not a concern here.
Early June in Snowdonia is experiencing a prolonged unsettled spell; while summer conditions should improve eventually, the current pattern shows no sign of stabilising until possibly June 13–14.
Contributing Factors
6
Over 75mm has fallen in the past 7 days with rain on every single day, keeping rock surfaces persistently wet.
Average humidity of 86% over the last week severely inhibits surface evaporation even between showers.
Rain fell early this morning and a 2.8mm shower is forecast at 16:00 with further light rain into the evening, eliminating any useful drying window.
Winds of 23–28 km/h provide some air movement, but at this humidity level wind alone cannot dry saturated surfaces between rain events.
Rhyolite does not absorb water, so there is no structural damage risk and the rock will dry quickly once a sustained dry spell arrives.
The next three days (June 10–12) forecast a further 26mm of rain, extending the wet period with no drying opportunity.
Recommendations
3
- Wait for the forecast dry spell beginning around June 13–14, which should allow surfaces to dry within a few hours given the warmer temperatures and lower humidity.
- If visiting on June 13, check the boulders for residual seepage and test friction on easier problems before committing to anything harder.
- Monitor the forecast closely as Snowdonia weather can change rapidly — a dry morning window on June 14 looks most promising for good conditions.
Do Not Climb
92%
9 days ago
The RAC Boulders are currently soaked after a prolonged wet spell — 67.9mm in the last 7 days including 20.8mm today — and the rock will be wet and slippery. Although rhyolite doesn't suffer structural damage, there is no safe friction available right now and rain continues in the forecast for the coming days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The RAC Boulders sit at road level near Llynnau Mymbyr and can collect runoff and ground moisture from the surrounding hillside, prolonging surface wetness even after rain stops.
- The west-facing aspect means afternoon sun can help dry surfaces, but persistent cloud cover and high humidity (87% average this week) are severely limiting evaporation.
- Being roadside boulders with flat grassy landings, the ground beneath problems will be saturated and muddy, making safe spotting and landing difficult.
- Some of the lower boulders near the lake edge can remain damp longer due to proximity to water and sheltered positions among trees.
Warnings
2
- Rhyolite becomes extremely slippery when wet — friction-dependent slab and wall problems at RAC Boulders will be dangerous.
- Saturated grassy landings increase the risk of ankle injuries on even low-level problems.
Reasoning
The rock is currently wet from heavy and persistent rainfall — 20.8mm today alone on top of nearly 68mm over the past week — and surfaces will have no usable friction.
Despite partial wind exposure and a west-facing aspect, the continuous rain, high humidity (87% average), and full cloud cover have prevented any meaningful drying; even the brief dry window this afternoon (07:00–17:00) is insufficient given the saturation.
Rhyolite is non-porous so there is no risk of structural weakening or hold breakage from the wet conditions.
Early June in Snowdonia often brings unsettled Atlantic weather; temperatures around 12°C are below average and slow evaporation, though freeze-thaw is not a concern at this time of year.
Contributing Factors
6
67.9mm in the last 7 days with 20.8mm today means the rock surfaces are thoroughly wet.
Rain is forecast every day through June 12th, preventing any sustained drying period.
Average humidity of 87% over the past week and 80%+ forecast severely limits surface evaporation.
SW winds of 20–30 km/h provide some air movement but are insufficient to dry saturated surfaces between rain events.
Temperatures around 12°C are below average for early June and slow evaporative drying.
Rhyolite does not absorb water so will dry relatively quickly once a sustained dry period arrives — the issue is purely surface friction.
Recommendations
3
- Do not climb today — the rock is wet and slippery after heavy rain; wait for a sustained dry spell.
- Monitor conditions from June 13th onwards when the forecast shows a possible dry window developing.
- If visiting in the coming days, consider alternative indoor climbing at nearby walls rather than risking a session on greasy rhyolite.
Do Not Climb
92%
10 days ago
The RAC Boulders are currently saturated after 82mm of rain in the past 7 days, with 14mm falling today and heavy rain forecast to continue tomorrow. Rhyolite becomes extremely slippery when wet, and there is no realistic drying window in the coming days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The RAC Boulders sit at roadside level in the Ogwen/Mymbyr valley corridor, which funnels prevailing SW winds and associated moisture directly onto the west-facing rock.
- Some boulders have overhanging faces and sheltered undersides that can remain climbable in light drizzle, but the sustained heavy rainfall makes even these unlikely to be dry.
- The flat grassy landings around the boulders will be waterlogged after this prolonged wet spell, adding slip and injury risk on approaches and spotting positions.
- Roadside drainage and runoff from the hillside above can channel water across certain boulder bases, compounding surface moisture on lower problems.
Warnings
2
- Wet rhyolite is exceptionally slippery — even apparently dry-looking surfaces can have a moisture film that eliminates friction without warning.
- Waterlogged grassy landings significantly increase the risk of ankle and knee injuries from slips during bouldering falls.
Reasoning
With 82mm in the past 7 days, 14mm today, and 94% humidity, all boulder surfaces will be thoroughly wet with no chance of drying.
Zero consecutive dry days combined with persistent SW winds carrying moisture mean no meaningful drying has occurred or will occur imminently.
Rhyolite is non-porous and not at risk of structural damage from moisture, so the concern is purely friction loss and climber safety.
Early June in Snowdonia is experiencing an unusually wet and cool spell, with temperatures well below seasonal averages and persistent Atlantic fronts.
Contributing Factors
6
82mm in the past 7 days with 14mm today ensures all surfaces are thoroughly wet.
Average humidity of 90% over the past week prevents effective evaporation even between showers.
Zero consecutive dry days means the rock has had no opportunity to dry at all.
Averaging just 12.4°C over the past week significantly slows any surface evaporation.
Wind aids drying but the prevailing SW direction drives moisture directly onto the west-facing boulders.
67mm forecast over the next 6 days with no meaningful dry window until possibly June 13.
Recommendations
3
- Do not visit until there have been at least 1–2 full dry days with lower humidity; the earliest realistic window may be June 13 or later.
- If in the area, consider indoor climbing at Beacon Climbing Centre in Caernarfon as an alternative.
- Monitor conditions closely via UKC and local social media for real-time reports before making any trip.
Do Not Climb
92%
11 days ago
The RAC Boulders are currently wet and unsuitable for climbing. Nearly 72mm of rain has fallen in the last 7 days alone, including significant downpours on June 1st (31mm) and June 3–4th (27mm combined), with further rain today and heavy rain forecast for the next two days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The boulders sit in the Mymbyr valley floor at 200m, where humidity and valley-bottom moisture linger longer than at exposed higher crags.
- West-facing aspect means the boulders only receive afternoon and evening sun, limiting the drying window — especially problematic given the current short dry spells between showers.
- Some boulders near the lakeside can accumulate ground moisture and splash from saturated grassy landings, adding to the wet feel even after surface rock begins to dry.
- Being roadside and beginner-friendly, this venue attracts climbers who may not recognise that rhyolite — while structurally unaffected by water — becomes dangerously slippery when wet, particularly on the lower-grade slabby problems.
Warnings
2
- Rhyolite is extremely slippery when wet — friction loss on slab and wall problems creates a serious fall risk, especially for the lower-grade climbers this venue attracts.
- Grassy landings may be waterlogged and unstable after prolonged rain, reducing the effectiveness of crash pads.
Reasoning
With 72mm in the past week, 5.9mm today, and 97% humidity recently, the rock surfaces are currently wet and will have residual surface moisture in crevices and on shaded faces.
Zero consecutive dry days and only partial wind exposure mean no meaningful drying has occurred; the west aspect limits sun exposure to afternoons, and persistent SW winds have been accompanied by repeated rain rather than aiding evaporation.
Rhyolite is non-porous and structurally unaffected by moisture, so hold breakage and rock damage are not concerns here.
Early June in Snowdonia is prone to prolonged wet spells with Atlantic fronts, and current conditions reflect an active unsettled pattern with below-average temperatures limiting evaporation.
Contributing Factors
6
Nearly 72mm in the last 7 days with significant events on June 1st (31mm), June 3rd (11mm), and June 4th (16mm) has kept surfaces persistently wet.
5.9mm falling today with 17.9mm forecast tomorrow means no drying window is available in the immediate term.
Average humidity of 89% over the past week, peaking at 97%, severely inhibits surface evaporation even during rain-free hours.
Winds of 20–37 km/h provide some air movement but are arriving with moisture-laden Atlantic air, so their drying benefit is minimal.
Rhyolite does not absorb water, so once a genuine dry spell arrives the surfaces will dry within hours rather than days.
Average temperatures around 13°C are below seasonal norms, slowing evaporation and extending surface drying times.
Recommendations
3
- Wait for at least a full dry day with humidity below 80% before visiting; rhyolite dries quickly once conditions allow but currently no such window exists.
- Monitor forecasts closely — the earliest potential window may emerge around June 12th if the forecast dry day materialises, but check updated forecasts before travelling.
- If you do visit during a dry spell, test friction carefully on an easy problem first, as shaded or north-facing sides of boulders may retain surface moisture longer than the west-facing surfaces.
Climbing Outlook