Condition Analysis
AI-powered assessment using site data and 14-day weather history
Today is the first dry day after a very wet week (51.8mm in 7 days), with the last rain falling early on April 12. The south-facing aspect and moderate winds should have dried exposed surfaces, but seepage, sheltered areas, and high ambient humidity mean conditions need on-ground verification before committing to climb.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Wavelength Boulders sit on the south side of the Llanberis Pass above the Cromlech hut — the south-facing aspect receives good solar radiation from mid-morning, which will have aided drying through yesterday afternoon and today.
- The stratified rhyolite formations here can channel seepage along horizontal bands after prolonged wet spells; with over 50mm in the past week, some problems may have active seepage lines even though surface rock appears dry.
- The 15–20 minute uphill approach at 300m altitude means conditions can be noticeably cooler and damper than roadside venues in the Pass — overnight humidity was high (up to 89%) and condensation may linger on north-facing facets of boulders.
- The heavy rain on April 11 (31.6mm) will have saturated the ground and surrounding vegetation, contributing to localised humidity and slow ambient drying around the boulder field.
Warnings
2
- Do not climb on any surface that appears damp or greasy — wet rhyolite loses friction dramatically and a slip at even bouldering height can cause serious injury.
- Check BMC RAD for nesting restrictions in the Llanberis Pass area, as peregrine and raven nesting season runs February–June.
Reasoning
Rain last fell in the early hours of April 12 (4.8mm total that day, mostly before 06:00), giving roughly 30+ hours of drying by this afternoon, but the preceding week dumped over 50mm and the ground is thoroughly saturated.
The south-facing aspect and moderate southerly winds (18–27 km/h) through yesterday afternoon into today should have cleared exposed surfaces, though humidity remained high overnight (76–89%) limiting drying of sheltered faces.
Rhyolite is non-porous and does not suffer structural weakening when wet — the risk here is purely friction loss from residual surface moisture, not hold breakage.
Early April in Snowdonia is a transitional period with unpredictable weather; the recent pattern of repeated frontal rain with short dry windows is typical of spring in the Pass, and the forecast shows more rain arriving tomorrow.
Contributing Factors
7
Over 50mm fell in the past 7 days including 31.6mm on April 11, thoroughly saturating the ground and potentially activating seepage lines across the boulder field.
No rain has fallen since early April 12, giving approximately 30+ hours of drying time on a non-porous rock type that sheds surface water relatively quickly.
The south aspect maximises solar exposure during spring daylight hours, significantly accelerating surface drying on directly exposed faces.
Southerly winds of 18–23 km/h provide reasonable airflow across the boulders, aiding evaporation of surface moisture.
Humidity has averaged 76% over the past week and reached 89% overnight, slowing drying and raising the risk of condensation on cooler rock surfaces.
The 135.7mm of rain over the past 28 days has left the hillside thoroughly waterlogged, contributing to localised seepage and elevated humidity around the boulders.
The forecast shows 11.3mm tomorrow and further heavy rain (18.9mm) on April 15, meaning today is a narrow dry window before conditions deteriorate again.
Recommendations
3
- Visit this afternoon when solar heating has maximised drying on south-facing faces, and physically touch the rock before committing — if it feels cold and clammy, walk away.
- Focus on the most exposed, south-facing problems and avoid any lines with visible seepage, dark wet streaks, or lichen that looks freshly dampened.
- Bring a towel and brush but be realistic — if more than a handful of problems are damp, conditions aren't truly climbable and it's better to wait for a longer dry spell.
Previous Analyses
Do Not Climb
92%
2 days ago
The Wavelength Boulders are currently wet and unsuitable for climbing. Heavy rain yesterday (31.6mm) followed by further rain today (4.5mm) means the rock will be saturated with surface moisture, and the forecast offers no meaningful drying window over the coming days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach above the Climbers' Club hut means seepage from saturated ground above can feed moisture onto boulder faces for extended periods after heavy rain, particularly on overhanging and roofed features.
- The south-facing aspect would normally aid drying, but persistent cloud cover, high humidity (80%), and ongoing precipitation today negate any solar benefit.
- The stratified rhyolite formations at Wavelength can trap water in horizontal breaks and seepage lines between layers, meaning even after surface drying some problems — especially slabs and vertical faces — may retain damp patches.
- At 300m altitude in early April, overnight temperatures near 4°C combined with high humidity can produce condensation on rock surfaces even during nominally dry spells, further delaying effective drying.
Warnings
3
- Wet rhyolite is extremely slippery — friction loss on the Wavelength Boulders in these conditions creates serious fall and injury risk.
- The uphill approach will be muddy and potentially slippery given the saturated ground; take care even if just walking up to inspect conditions.
- Check BMC RAD for any bird nesting restrictions — peregrine and raven restrictions may be active at nearby crags in April.
Reasoning
With 31.6mm yesterday, 4.5mm today, and 51.5mm in the last seven days, the rock surfaces are currently wet and the surrounding ground is thoroughly saturated.
Zero consecutive dry days and persistent SW winds with 80% humidity mean no meaningful drying has occurred; the south aspect cannot compensate when the rock is actively being rained on.
Rhyolite is non-porous and does not suffer structural damage when wet, so hold breakage and rock conservation are not concerns here.
Early April in Snowdonia is a transitionally wet period with short days and cool temperatures at 300m; the current pattern of repeated Atlantic fronts is typical and unlikely to break soon.
Contributing Factors
7
31.6mm fell yesterday and 4.5mm today, with 51.5mm over the past week — the rock is actively wet.
There has been no dry day to begin drying; today itself has 4.5mm of rain.
Humidity at 80% today and averaging 75% over the past week severely limits evaporative drying.
The south aspect is normally beneficial for drying, but cloud cover and active rain negate this advantage today.
Partial wind exposure at 26 km/h SW provides some airflow, but cannot dry rock that is still receiving rain.
55.1mm forecast over the next six days including a major 34.4mm event on April 15th means no sustained drying window is in sight.
Rhyolite does not absorb water or weaken structurally, so once rain stops and a dry window arrives, surface drying can be relatively quick.
Recommendations
3
- Do not climb today — the rock is wet and rhyolite friction is severely compromised in these conditions.
- Monitor conditions closely; the earliest plausible window would require at least a full dry day with sun and wind, which the forecast does not show before April 18th at the earliest.
- Consider lower-altitude indoor walls or slate sport venues with large overhangs as alternatives until a proper drying window materialises.
Do Not Climb
95%
3 days ago
Wavelength Boulders are currently receiving heavy rain (24.3mm today) following a very wet week, making conditions completely unsuitable for climbing. The rhyolite will be saturated on the surface and extremely slippery, with no drying window in sight.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means the boulders sit in an exposed hillside position where today's 35+ km/h southerly winds will drive rain directly onto the south-facing rock surfaces.
- The stratified formations at Wavelength create horizontal ledges and seepage lines that trap and channel water after heavy rain, requiring extended dry periods before moisture fully clears from holds and features.
- South-facing aspect is normally an advantage for drying, but with persistent southerly and south-westerly weather systems this week, the aspect has been receiving wind-driven rain head-on rather than benefiting from sheltered drying.
- At 300m altitude in early April, overnight temperatures near 3°C combined with high humidity (82%) mean overnight dew and condensation will further inhibit drying even during brief dry spells.
Warnings
2
- Active heavy rainfall (24.3mm) makes all rhyolite surfaces extremely slippery — climbing today risks serious injury from friction loss.
- The uphill approach to Wavelength Boulders will be waterlogged and potentially hazardous in strong winds (35+ km/h); take care on the hillside.
Reasoning
The rock is thoroughly wet from 24.3mm of rain today on top of 40.7mm in the past week, with zero consecutive dry days — surface moisture will be extensive across all problems.
Despite strong southerly winds (35.6 km/h), the south-facing aspect is being hit directly by wind-driven rain today, and there has been no meaningful drying window since the last significant rainfall on April 9–10.
Rhyolite is non-porous and does not suffer structural damage when wet, so there is no hold breakage or rock conservation concern — the issue is purely friction and safety.
Early April in Snowdonia is a notoriously wet period with unstable Atlantic weather patterns; temperatures averaging 8.4°C and humidity averaging 74% over the past week provide poor drying conditions.
Contributing Factors
6
24.3mm of precipitation today is a substantial downpour that will leave all rock surfaces thoroughly wet and streaming.
40.7mm over the past 7 days with zero consecutive dry days means the rock has had no opportunity to dry out.
82% humidity today and averaging 74% over the past week severely limits evaporative drying of surface moisture.
35.6 km/h southerly winds are driving rain directly onto the south-facing boulders rather than aiding drying.
The next 5 days forecast a further 50.6mm of rain with no extended dry window, meaning conditions will not materially improve.
Rhyolite does not absorb water or suffer structural weakening, so it will dry relatively quickly once rain stops and conditions allow.
Recommendations
3
- Do not visit Wavelength Boulders today — the rock will be dangerously slippery with active rainfall and no friction.
- Monitor the forecast for a sustained dry window of at least 24 hours with low humidity before planning a return visit.
- If visiting the Llanberis Pass area, consider using the time for route planning or checking BMC RAD for any seasonal bird nesting restrictions that may apply.
Do Not Climb
85%
4 days ago
The Wavelength Boulders are currently wet following 9.8mm of rain yesterday and 2.3mm today, with zero consecutive dry days. Despite rhyolite's quick-drying properties, the rock surface will still be damp and slippery, and a massive 26.3mm of rain is forecast for tomorrow — conditions are clearly unsuitable for climbing today and will worsen before they improve.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means the boulders sit at ~300m on the south side of the Pass, where orographic uplift from prevailing SW winds concentrates rainfall well above the valley floor figures.
- The stratified rhyolite formations at Wavelength can hold surface moisture in horizontal seepage lines and layered features, meaning even after general surfaces dry, specific problems may retain dampness longer.
- The south-facing aspect is beneficial for solar drying in spring, but with the sun still relatively low and recent persistent cloud cover, solar gain has been limited.
- The venue's partial wind exposure from the prevailing SW/S winds will aid drying when rain stops, but the consistently high humidity (72–93% over recent days) reduces evaporative drying efficiency.
Warnings
2
- Wet rhyolite is extremely slippery — friction loss on the steep and technical problems at Wavelength creates a serious fall risk.
- The uphill approach to 300m may be boggy and slippery after sustained rain; take care on the hillside path.
Reasoning
The rock is currently wet — 9.8mm fell on April 9th and 2.3mm today (April 10th), with zero consecutive dry days and ambient humidity at 72%.
Despite the south aspect and moderate S wind at 31 km/h, the lack of any dry window since April 8th and high recent humidity mean surface moisture has had no opportunity to fully evaporate.
Rhyolite is non-porous and does not suffer structural damage when wet, so hold breakage and rock conservation are not concerns here.
Early April in Snowdonia brings frequent Atlantic frontal systems; the 120mm over 28 days is typical for spring in the Pass, and the forecast shows another heavy pulse tomorrow (26.3mm) before any meaningful dry spell.
Contributing Factors
6
9.8mm yesterday and 2.3mm today with zero consecutive dry days means the rock surface is actively wet.
A substantial 26.3mm is forecast for April 11th, which will saturate the crag and reset any drying progress.
Humidity has averaged 75% over the past week and is 72% today, significantly slowing evaporative drying.
The south-facing aspect and 31 km/h southerly wind would promote rapid drying if rain ceased, but cannot overcome active precipitation.
Rhyolite does not absorb water so will dry quickly once conditions allow, but surface friction is severely reduced when wet.
120mm over the past 28 days reflects an unsettled Atlantic pattern with limited sustained dry windows for thorough drying.
Recommendations
3
- Do not visit today — the rock is wet and slippery, with further heavy rain forecast tomorrow.
- Monitor conditions from April 13th onwards when a brief drier window may begin, but verify on arrival given the saturated surroundings.
- Consider lower-altitude, sheltered alternatives in the Pass if desperate to climb, but even roadside venues will be affected by the current wet spell.
Do Not Climb
45%
5 days ago
Today has seen 1.1mm of rain on top of a very wet recent period (21mm in 7 days, 137mm in 28 days), and the rock has had zero consecutive dry days. Although rhyolite dries relatively quickly, the combination of today's precipitation, high humidity (81%), and overnight condensation from near-saturating conditions means surfaces are likely damp and friction will be compromised.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means the boulders sit at ~300m where cloud and mist can linger even when the valley floor is clear, increasing surface moisture from condensation.
- The south-facing aspect is beneficial for solar drying, but today's overcast skies and light rain limit its effectiveness — the excellent dry spell from April 6–8 has been interrupted.
- Stratified rhyolite formations can hold water in horizontal seepage lines between layers; after 137mm in 28 days, these seepage zones may still be weeping even when main surfaces appear dry.
- The Llanberis Pass funnels prevailing SW winds effectively, and today's 27 km/h SW wind will aid surface drying, but humidity remains too high for reliable evaporation.
Warnings
2
- Rhyolite becomes very slippery when wet — friction-dependent problems (slabs, smears) should be avoided entirely in current conditions.
- The saturated hillside and active seepage lines from 137mm of recent rainfall may cause localised weeping on stratified rock faces even when the main surface appears dry.
Reasoning
After 1.1mm of rain today following only a brief 2-day dry window (April 6–8), and with overnight humidity peaking at 95%, rock surfaces are very likely damp with residual moisture and condensation.
The south aspect and moderate SW wind (27 km/h) would normally promote quick drying on rhyolite, but today's rain, 81% average humidity, and overcast skies severely limit drying potential.
Rhyolite is non-porous and does not suffer structural weakening when wet, so hold breakage and rock damage are not a concern.
Early April in Snowdonia is transitional with unpredictable weather; the recent pattern of heavy Atlantic fronts interspersed with brief dry spells is typical, and overnight temperatures near 4°C slow evaporation.
Contributing Factors
6
1.1mm of precipitation today has interrupted the brief 2-day dry window from April 6–8, resetting surface conditions.
Humidity reached 93–95% overnight and into this morning, likely depositing condensation on rock surfaces at 300m altitude.
137mm over 28 days and 21mm in the last 7 days means the hillside is saturated and seepage lines are likely active.
The south-facing aspect and 27 km/h SW wind provide reasonable drying potential when the rain stops and sun breaks through.
Rhyolite does not absorb water, so surfaces can dry within hours given favourable conditions — no structural damage risk.
Two fully dry days (April 6–7) with warm temperatures (up to 19.7°C) and low humidity (45%) would have dried most surfaces before today's rain.
Recommendations
3
- Wait for a sustained dry spell of at least 24 hours with low humidity before visiting; today's conditions are unlikely to yield reliable friction.
- If you do visit, test friction carefully on low, safe problems before committing to anything steep or technical — the rhyolite can feel deceptively grippy until loaded.
- Check BMC RAD for any active bird nesting restrictions in the Llanberis Pass area, as peregrine nesting season is underway (February–June).
Likely Safe to Climb
82%
6 days ago
Three consecutive dry days including yesterday's exceptional drying conditions (19.7°C, 45% humidity, 31 km/h SE wind) have thoroughly dried the south-facing rhyolite at Wavelength Boulders. Surface friction should be excellent today, though humidity is rising and rain returns tomorrow — this is likely the last good window for several days.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The south-facing aspect at 300m received strong solar radiation during yesterday's warm spell, accelerating surface drying significantly on the non-porous rhyolite.
- The stratified formations at Wavelength can hold residual seepage in horizontal breaks and overlaps after prolonged wet spells — check any features with horizontal cracks or layered overhangs for lingering damp.
- The 15–20 minute uphill approach means conditions at the boulders may differ from what you see at road level in the Pass — it's cooler and more exposed at 300m, which aids drying via wind but can mean cloud/mist contact.
- Spring bird nesting restrictions may apply to nearby crags in the Llanberis Pass — check BMC RAD for any current seasonal closures in the area before heading up.
Warnings
2
- Rain returns tomorrow (April 9th) and persists through April 13th — plan accordingly as conditions will deteriorate rapidly.
- Humidity is higher today than yesterday; friction will be noticeably reduced compared to yesterday's exceptional conditions.
Reasoning
After three fully dry days — including an outstanding drying day on April 7th with very low humidity (40–47%) and warm temperatures up to 19.7°C — the non-porous rhyolite surface should be thoroughly dry.
The south-facing aspect combined with yesterday's SE winds at 31 km/h and sub-50% humidity would have driven rapid evaporation; even residual dampness from the 1mm rain on April 5th should be long gone.
Rhyolite is non-porous and does not suffer structural weakening when wet, so there is no hold breakage concern.
Early April in Snowdonia is transitional — the recent warm spell is unusual and conditions will deteriorate sharply from tomorrow with a return to typical unsettled spring weather.
Contributing Factors
6
No precipitation since April 5th (1.0mm trace), giving ample time for non-porous rhyolite to shed all surface moisture.
April 7th brought 19.7°C, humidity as low as 38%, and 31 km/h winds — outstanding drying conditions for any rock type.
The south aspect maximises solar gain during the spring days, accelerating surface evaporation particularly during the recent clear spell.
Today's humidity has risen to 81% with lighter winds at 17.6 km/h, which won't re-wet the rock but means friction may feel marginally less sharp than yesterday.
138.7mm over 28 days is significant, but rhyolite is non-porous so prolonged saturation of the rock mass is not a concern — only surface and seepage moisture matters.
3.1mm forecast for April 9th marks the start of a wet spell through to April 13th, making today likely the last good climbing window.
Recommendations
3
- Climb today if possible — this is likely the last dry window before an extended wet spell lasting through at least April 13th.
- Check stratified layers and horizontal breaks for any residual seepage before committing to harder problems, particularly on shaded or overhanging faces.
- Bring a towel and brush to manage any localised damp patches; conditions are best during the warmest part of the afternoon when solar heating is strongest.
Marginal — Assess Conditions
62%
8 days ago
After a very wet late March and early April, today marks only the second consecutive dry day with improving conditions — warm southerly sun (13.7°C), dropping humidity (70%), and moderate wind should be drying the south-facing rhyolite surfaces. However, given 29.8mm in the last 7 days including rain as recently as April 5th, and the high ambient humidity of the preceding weeks, seepage and residual dampness in sheltered areas are likely; climbers should visually assess conditions on arrival.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- Wavelength Boulders sit above the Cromlech Boulders on the south side of the Pass with a south-facing aspect, meaning they receive direct afternoon sun which significantly aids drying — but the 15–20 minute uphill approach means the boulders sit at ~300m where cloud and mist can linger even when the road is dry.
- The stratified rhyolite formations here have horizontal layering that can trap and channel water along seepage lines, particularly on overhanging faces and roofs where water weeps from cracks above — these features will be the last to dry after the prolonged wet spell.
- The hillside location above the Climbers' Club hut means drainage from higher ground can keep the base areas and lower-angled slabs damp even when vertical faces have dried.
- Several classic problems including steeper lines may dry faster due to their angle shedding water, but slabbier problems relying on friction will be most affected by any residual surface moisture.
Warnings
2
- Rhyolite becomes extremely slippery when damp — do not commit to friction-dependent moves unless the rock is confirmed dry by touch.
- The prolonged wet spell means the uphill approach path will be muddy and potentially slippery; take care on the steep hillside access.
Reasoning
The rock received 1.0mm on April 5th and 9.8mm the day before, with only one full dry day elapsed; surface moisture on exposed south-facing vertical and steep faces is likely evaporating, but sheltered, lower-angled, and seepage-prone features will still hold dampness.
The south aspect, moderate westerly-to-southerly wind (~23 km/h), and today's warm temperatures (13.7°C) with 70% humidity provide reasonable drying conditions for non-porous rhyolite, but only ~18 hours of effective drying have occurred since the last light rain on April 5th evening.
Rhyolite is non-porous and does not suffer structural weakening when wet, so hold breakage and rock damage are not concerns here.
Early April in the Llanberis Pass is transitional — days are lengthening and solar angle is improving for south-facing crags, but the recent pattern of persistent wet Atlantic weather with high humidity (84% average over 7 days) means the general environment remains damp and drying is slower than summer conditions would allow.
Contributing Factors
8
29.8mm fell in the last 7 days with rain on 5 of those days, and 164.4mm over the last 28 days — the ground and surroundings are thoroughly saturated, contributing to ambient moisture.
Just one consecutive dry day since light rain (1.0mm) on April 5th is marginal for complete surface drying, especially in sheltered spots and seepage areas.
Warm temperatures (13.7°C), dropping humidity (70%), moderate southerly wind (22.7 km/h), and direct sun on this south-facing crag provide good active drying conditions today.
The south aspect maximises solar exposure during April's improving sun angle, accelerating evaporation on exposed faces.
Rhyolite does not absorb water so only surface moisture needs to evaporate, meaning drying times are shorter than for sandstone or gritstone.
The 7-day average humidity of 84% and overnight humidity reaching 89% slows evaporation and can cause condensation on cold rock surfaces in early morning.
Prolonged wet weather has saturated the hillside above, meaning seepage lines and drainage channels through the boulderfield may still be active.
Tomorrow forecasts 19.4°C with 55% humidity and no rain, which will provide excellent further drying if today's conditions hold.
Recommendations
3
- Visit in the afternoon when the south-facing rock has had maximum solar exposure and drying time — avoid early morning when overnight condensation may be present.
- Prioritise steep and overhanging problems which shed water fastest; avoid slabs and friction-dependent lines unless visibly bone-dry, as even slight dampness on rhyolite dramatically reduces friction.
- Check seepage lines and horizontal breaks carefully before committing — the stratified formations can channel hidden moisture from saturated ground above.
Do Not Climb
70%
9 days ago
The Wavelength Boulders have had a very wet recent period with 30mm in the last 7 days and nearly 10mm falling yesterday alone, followed by only light precipitation today (1.2mm) in still-humid conditions. With zero consecutive dry days and high recent saturation, surface moisture and seepage are highly likely despite rhyolite's non-porous nature.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means the boulders sit above the valley floor where seepage from saturated hillside soils above can persist for days after heavy rain, feeding moisture onto boulder tops and overhangs.
- The south-facing aspect is beneficial for solar drying, but early April sun angles and today's overcast/windy conditions limit effective solar gain at 300m altitude.
- The stratified rhyolite formations at Wavelength can channel water along horizontal bedding planes, creating persistent damp bands even when the main face appears dry.
- The Llanberis Pass funnels weather from the southwest, and the prolonged SW/W wind pattern of recent weeks has delivered sustained moisture to this side of the pass.
Warnings
2
- Rhyolite becomes extremely slippery when wet — a fall from even modest boulder heights onto wet ground can cause serious injury.
- The hillside approach may be boggy and slippery after sustained rain; take care on the walk-in.
Reasoning
With 9.8mm on April 4th, 9.3mm on April 3rd, 7.0mm on April 2nd, and 1.2mm today, the rock surfaces are almost certainly still damp, and surrounding ground will be thoroughly saturated feeding ongoing seepage.
Today's westerly wind at 31.7 km/h provides decent surface drying, but with only a few hours since the last precipitation and humidity at 73%, effective drying has barely begun and is insufficient to clear moisture from crevices and seepage lines.
Rhyolite does not suffer structural damage when wet, so there is no hold-breakage or rock-conservation concern — the issue is purely friction and safety.
Early April in Snowdonia is a transitional period with short drying windows, frequent Atlantic fronts, and limited solar intensity; the ground and hillside remain saturated from a very wet March (164.7mm in 28 days).
Contributing Factors
7
Nearly 27mm fell over April 2–4 with 1.2mm today, giving zero consecutive dry days and ensuring widespread surface moisture.
164.7mm over 28 days has thoroughly saturated the hillside, increasing the likelihood of persistent seepage onto boulders from above.
Today's 31.7 km/h westerly wind helps surface evaporation, though it cannot address seepage or sheltered faces.
The south aspect receives the best available solar radiation for drying, though early April sun at 300m is limited in intensity.
Average humidity over the last 7 days is 85%, and today's 73% — while the lowest recently — still limits evaporative drying efficiency.
Rhyolite does not absorb water internally, so once surface moisture and seepage clear, the rock will offer excellent friction.
At 300m with a max of only 6.3°C today, temperatures are too low to drive rapid evaporation of standing moisture.
Recommendations
3
- Wait for at least one full dry day with good sun before visiting — April 7th looks the most promising window this week.
- If you do visit, test friction carefully on low easy problems before committing to anything steep or technical; retreat if holds feel greasy.
- Check seepage lines along the stratified bands and around boulder tops — these can remain wet long after exposed faces appear dry.
Do Not Climb
30%
10 days ago
Today has seen nearly 5mm of rain with high humidity (87%) and strong southerly winds, following a very wet week with 32mm in the last 7 days. The rock will be wet or damp right now; rhyolite dries quickly but conditions today are not suitable for bouldering.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The south-facing aspect and 300m altitude mean seepage from the saturated hillside above can persist on certain problems even after surface moisture has dried, particularly on lower-tier boulders.
- The uphill approach on wet ground after prolonged rain will be slippery and muddy — take care on the path from the Climbers' Club hut, especially descending.
- The stratified rhyolite formations can channel and trap water in horizontal breaks and overlap features, creating localised damp patches that persist longer than open faces.
- Strong southerly winds today (39 km/h) will aid surface drying but at this aspect they can also drive rain directly onto the south-facing boulder faces.
Warnings
2
- Rhyolite becomes dangerously slippery when wet — bouldering on damp holds risks uncontrolled falls and injury.
- The approach path will be very muddy and slippery after prolonged rain; take extra care especially on the descent.
Reasoning
With 4.9mm of rain today on top of 32mm in the past week and 87% humidity, the rock surfaces are currently wet or at best very damp.
Strong southerly winds (39 km/h) and the south-facing aspect would normally promote rapid drying, but today's ongoing rain and high humidity negate this advantage — meaningful drying cannot begin until precipitation stops.
Rhyolite is non-porous and not at risk of structural damage from moisture; the concern here is purely friction loss and climber safety on wet or greasy holds.
Early April in Snowdonia is a transitional period with frequent Atlantic weather systems; the persistently high humidity (86% average over 7 days) and regular rain are typical and slow drying at 300m altitude.
Contributing Factors
6
4.9mm today plus 32mm over the past 7 days means rock surfaces are wet, with zero consecutive dry days recorded.
Average humidity of 86% over the last week and 87% today severely limits evaporative drying.
39 km/h winds would normally aid drying on this partially exposed site, but southerly direction drives moisture directly onto the south-facing boulders during active rain.
The south aspect receives good solar radiation and will promote rapid drying once rain stops and skies clear.
Rhyolite does not absorb water, so once rain ceases and humidity drops, surface moisture can evaporate within hours in favourable conditions.
158.6mm of rain in the past 28 days has thoroughly saturated the hillside, increasing the risk of seepage onto boulder faces from above.
Recommendations
3
- Wait for at least a full dry day with lower humidity before visiting — the forecast suggests April 6th or 7th could offer good conditions.
- If visiting soon, bring a towel and brush to check rock texture; if holds feel greasy or polished rather than grippy, do not commit to problems.
- Check the BMC RAD for any seasonal bird nesting restrictions in the Llanberis Pass area before heading out.
Do Not Climb
92%
11 days ago
Wavelength Boulders are currently wet and unsuitable for climbing. Today has seen 15.1mm of rain with 91% humidity, following a prolonged wet period with 33.3mm in the last 7 days and nearly 165mm over the past month — the rock will be thoroughly saturated on the surface and seepage lines will be active.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means the boulders sit above the valley floor at ~300m where cloud base and orographic rainfall often keep surfaces damp longer than roadside venues.
- The stratified rhyolite formations at Wavelength can trap water in horizontal seams and overlaps, meaning even after surface drying some problems — particularly those with slopers or layered features — may retain residual moisture.
- The south-facing aspect is a significant advantage for drying when the sun appears, but in the current unsettled SW airflow pattern the aspect is also directly exposed to incoming rain-bearing weather.
- The Llanberis Pass funnels prevailing SW winds effectively, which aids drying but also channels moist Atlantic air directly onto these boulders during wet spells.
Warnings
3
- Active rainfall today makes all problems dangerously slippery — do not attempt to climb.
- The extended wet period means seepage lines in stratified features may persist even after a day of surface drying.
- Check BMC RAD for any seasonal bird nesting restrictions in the Llanberis Pass before visiting — peregrine and raven restrictions may apply from February to June.
Reasoning
With 15.1mm of rain today on top of 33.3mm in the past week and persistent high humidity (85% average, 91% today), the rock surface will be thoroughly wet with active runoff and seepage.
Zero consecutive dry days and no meaningful drying window in recent days means the rock has had no opportunity to shed surface moisture despite moderate wind exposure and a south-facing aspect.
Rhyolite is non-porous and does not suffer structural damage when wet, so there is no hold-breakage or rock-conservation concern — the risk is purely friction-related.
Early April in Snowdonia is a transitionally wet period with frequent Atlantic fronts; the prevailing SW pattern is bringing repeated rain events, and temperatures around 7–12°C provide only moderate evaporative potential.
Contributing Factors
6
15.1mm of precipitation today with 91% humidity means the rock is actively wet right now.
33.3mm over the past 7 days with no consecutive dry days means no drying window has occurred.
Average humidity of 85% over the past week severely limits evaporation even during brief dry spells.
The south aspect aids drying when conditions allow but currently faces directly into the prevailing SW rain-bearing weather systems.
Partial wind exposure and 28 km/h SW winds today would help drying in a dry spell, but are currently carrying moisture-laden air.
Rhyolite sheds water quickly once rain stops and will not suffer structural damage, but surface friction is severely compromised when wet.
Recommendations
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- Do not visit today — the rock is actively wet and rhyolite becomes dangerously slippery in these conditions.
- Monitor conditions for April 6th, which is the first forecast dry day with favourable southerly aspect and could offer a brief window if the morning is clear.
- If visiting the Llanberis Pass area in this weather, consider indoor alternatives at Beacon Climbing Centre in Caernarfon or The Indy in Llanberis.
Climbing Outlook