Condition Analysis
AI-powered assessment using site data and 14-day weather history
The rock has had roughly 24 hours of drying since the last light rain (1.3mm on May 6th), with today remaining dry and moderate southerly winds aiding evaporation on this south-facing venue. However, several days of light but persistent precipitation (May 1–6 totalling ~9.3mm) combined with high ambient humidity (~73–81%) mean some seepage areas and sheltered faces may still hold residual moisture.
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 cloud and mist can linger, potentially keeping humidity higher than valley-bottom readings suggest.
- Stratified rhyolite formations can trap water in horizontal seams and overlapping layers, creating localised seepage that persists well after exposed surfaces have dried.
- The south-facing aspect is a significant advantage for drying — solar radiation reaches these boulders through much of the day even in overcast spring conditions.
- Tomorrow (May 8th) brings 9.1mm of forecast rain, so today represents the best climbing window before another wet spell moves in.
Warnings
2
- Rain is forecast from tomorrow (May 8th, 9.1mm) through May 12th — today may be the last viable session for several days.
- High humidity at altitude may cause condensation on cold rock surfaces in early morning and evening; avoid these times.
Reasoning
Light but persistent rain over May 1–6 (totalling ~9.3mm across several days) followed by only one full dry day means surface moisture should be largely gone on exposed faces, but seepage lines and sheltered areas may still be damp.
The south aspect and moderate southerly wind (~14–18 km/h) have provided reasonable drying conditions over the past 24 hours, and today's forecast is entirely dry with humidity dropping to the low 60s by midday — adequate for surface drying of non-porous rhyolite.
Rhyolite is non-porous and does not suffer structural weakening when wet, so hold breakage is not a concern here.
Early May in Snowdonia is transitional — days are lengthening and temperatures are mild (~10–12°C), but persistent Atlantic moisture keeps humidity elevated and drying windows can be short-lived.
Contributing Factors
6
Multiple days of light precipitation from May 1–6 (totalling ~9.3mm) have kept the rock intermittently wet with limited drying windows.
Only one full dry day (May 6 borderline, today May 7 dry) has passed, which is likely sufficient for exposed rhyolite surfaces but marginal for sheltered spots.
The south-facing aspect receives good solar radiation and today's moderate southerly wind aids evaporation across exposed boulder faces.
Average humidity over the past week is 79%, and today's readings remain in the 63–76% range, slowing the final stages of drying.
Today is forecast completely dry, but 9.1mm of rain is expected tomorrow, making this a narrow climbing window.
Rhyolite does not absorb water so structural damage is not a concern — the risk is purely friction loss from surface moisture.
Recommendations
3
- Visit this afternoon (12:00–17:00) when humidity is lowest and the south aspect has had maximum solar exposure — visually inspect holds and test friction before committing to harder problems.
- Avoid seepage lines and problems within the stratified layering where water may still be weeping; stick to exposed, overhanging, or well-drained faces.
- Bring a towel and soft brush, and be prepared to walk away from individual problems that feel greasy — tomorrow's rain will reset drying progress.
Previous Analyses
Do Not Climb
35%
2 days ago
Light but persistent drizzle today combined with high humidity and overcast skies means the rhyolite surfaces at Wavelength are likely damp and slippery. Although there was a good dry spell in late April, the last week has seen repeated light rain events with no sustained drying, and today's forecast shows scattered showers through the afternoon.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means conditions at the boulders can differ from the road — the higher altitude (300m) keeps humidity elevated and temperatures cooler, slowing surface drying.
- South-facing aspect is advantageous when the sun breaks through, but today's 99–100% cloud cover negates most solar drying benefit.
- The stratified rhyolite formations can channel water along horizontal bedding planes, creating localised seepage that persists longer than the general surface moisture.
- Wavelength Boulders sit above the Llanberis Pass inversion layer on damp days — low cloud and mist can keep surfaces wet even without measurable rain.
Warnings
2
- Damp rhyolite is deceptively slippery — friction loss is severe even when surfaces appear only slightly moist, increasing the risk of unexpected slips on highball problems.
- A significant wet spell is forecast for May 9–10 (22mm+), so conditions will deteriorate further before improving.
Reasoning
Light rain on May 5th (1.6mm) and scattered showers today (1.5mm forecast) mean rock surfaces are currently damp, with no meaningful dry window to evaporate residual moisture.
Despite the south-facing aspect, persistent cloud cover (near 100%), light winds (5–14 km/h), and humidity around 75–85% today provide minimal drying potential — surface moisture from recent showers will linger.
Rhyolite is non-porous and structurally unaffected by moisture; the only risk is friction loss on wet or damp surfaces, which is significant for bouldering where falls are onto pads rather than ropes.
Early May in Snowdonia is transitional — days are lengthening but Atlantic weather systems still deliver frequent light rain, and 300m altitude keeps temperatures cool enough to slow evaporation.
Contributing Factors
6
Repeated light precipitation on May 1–3, May 5, and today (totalling ~9.5mm in the last week) has kept surfaces intermittently damp with no sustained drying period.
Hourly forecast shows 1.5mm of drizzle scattered across midday to late afternoon, preventing surfaces from drying even during the warmest part of the day.
Humidity of 73–89% and near-total cloud cover today severely limit evaporation, meaning even trace moisture will persist on rock surfaces.
The south-facing aspect would normally aid drying, but is rendered ineffective today by 99–100% cloud cover eliminating direct solar radiation.
Rhyolite does not absorb water so there is no structural risk, and surfaces will dry quickly once a genuine dry window with sun or wind arrives.
Winds of only 5–14 km/h at the boulders provide limited convective drying, insufficient to clear surface moisture between shower bursts.
Recommendations
3
- Wait for a sustained dry and sunny window — conditions could improve rapidly on rhyolite once the current unsettled spell passes.
- If you travel to the Pass today, consider walking the approach to scout conditions but be prepared to turn back if surfaces are visibly damp or greasy.
- Monitor the forecast for May 12th onwards, which may offer the first truly dry day after the incoming wet spell on May 9–11.
Marginal — Assess Conditions
72%
3 days ago
The rock has had two full dry days following light rain (2.3mm on May 3rd), and the south-facing aspect with moderate wind should have cleared surface moisture from exposed faces. However, persistent high humidity (70–91%) and heavy cloud cover today limit solar drying, so sheltered or north-facing features and seepage zones may still be damp — a visual check on arrival is warranted.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The uphill south-facing aspect means the main boulders receive good solar radiation when the sun breaks through, but today's heavy overcast (near 100% cloud until mid-afternoon) significantly reduces this advantage.
- Rhyolite's distinctive stratified formations at Wavelength can harbour moisture in horizontal layering and cracks even when the main face appears dry — check textured holds and horizontal breaks carefully.
- The 15–20 minute uphill approach means conditions at the boulders may differ from what you see at road level in the Pass; altitude (300m) brings cooler temps and potentially more residual dampness or mist.
- The heavy rain period from April 9–17 (over 80mm) may still be feeding hillside seepage lines near some boulders, even though recent precipitation has been light.
Warnings
1
- Condensation or residual dampness on sheltered faces could make holds unexpectedly slippery — test carefully before committing to highball problems.
Reasoning
The last meaningful rain was 2.3mm on May 3rd, followed by two dry days, and the non-porous rhyolite surface should be largely dry on exposed faces, though ambient humidity remains elevated (77% today).
Two consecutive dry days with the south-facing aspect and moderate northerly wind today should have evaporated surface water on open faces, but persistent cloud cover (near 100% through midday) has limited solar drying significantly.
Rhyolite is non-porous and does not suffer structural weakening when wet, so there is no hold breakage risk — the concern is purely friction loss on damp surfaces.
Early May in Snowdonia brings unpredictable weather with still-cool temperatures (~11°C average) and frequent cloud; the extended wet April (over 100mm in 28 days) means hillside drainage and seepage may persist longer than surface drying suggests.
Contributing Factors
6
No significant precipitation since May 3rd (2.3mm), giving the non-porous rhyolite ample time to shed surface water on exposed faces.
Humidity has been 75–91% through most of today, which slows evaporation and can leave a film of condensation on rock surfaces, particularly in sheltered spots.
Near 100% cloud cover through midday limits solar radiation on the south-facing boulders, reducing the key drying advantage of this aspect — though clearing is forecast from mid-afternoon.
The south-facing orientation combined with moderate northerly-to-easterly wind (14–17 km/h) provides reasonable airflow across the rock surface to assist drying.
Over 100mm fell in the past 28 days, meaning hillside groundwater is elevated and seepage lines near certain boulders could still be active.
Cloud cover is forecast to drop sharply from 15:00 onwards (to 20–0%), which combined with wind will provide a good drying and friction window in late afternoon.
Recommendations
3
- Target the late afternoon window (15:00–19:00) when cloud cover breaks and humidity drops to the low 60s — this will offer the best friction conditions today.
- Visually inspect holds and test friction on a known easy problem before committing to anything technical; pay particular attention to horizontal breaks and sheltered faces.
- Avoid any boulders near obvious seepage lines or drainage channels on the hillside, as the wet April may still be feeding these areas.
Marginal — Assess Conditions
68%
4 days ago
Light rain (2.3mm) fell yesterday with very high humidity (91%), but today is dry with moderate winds and the south-facing aspect should aid drying through the afternoon. Rhyolite doesn't absorb water, but residual surface dampness from yesterday's rain and persistent high humidity mean conditions should be visually checked on arrival before committing to harder problems.
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 higher on the hillside with better air circulation than roadside venues, aiding drying.
- The stratified formations at Wavelength can hold seepage in horizontal breaks and overlaps — inspect these features carefully as they take longer to dry than open faces.
- South-facing aspect receives good solar radiation even through cloud cover in May, but today's heavy cloud (70–90%) limits direct sun and slows surface evaporation.
- The extended wet spell from April 9–17 (over 80mm total) means the surrounding ground and moss are saturated, which can contribute ambient moisture and localised seepage even after the rock surface appears dry.
Warnings
1
- Residual dampness on rhyolite dramatically reduces friction — a surface that looks dry can still be greasy, so test carefully before attempting highball or technical problems.
Reasoning
Yesterday saw 2.3mm of rain ending by early morning, and humidity remained above 90% overnight; surface moisture from this light rain is likely still present in sheltered spots and cracks, though exposed south-facing surfaces may be drying by midday.
With only 1 full dry day, moderate northerly winds (~15 km/h), and the south-facing aspect receiving diffused solar radiation through heavy cloud, the main exposed faces should be approaching dry by early-to-mid afternoon, but sheltered features and horizontal breaks will lag behind.
Rhyolite is non-porous and does not suffer structural damage when wet — there is no hold breakage risk from climbing on damp rock, but friction is significantly reduced on wet surfaces.
Early May in Snowdonia is transitional with lengthening days providing reasonable drying hours, but the recent prolonged wet spell (100mm+ in 28 days) keeps ambient moisture high and ground saturated.
Contributing Factors
7
2.3mm fell on May 3rd with near-saturated humidity (91%), and only one dry day has elapsed since.
The south-facing orientation maximises solar exposure even through cloud, giving above-average drying potential for the Llanberis Pass.
Humidity is around 75–80% through most of today, slowing evaporation and potentially leaving a moisture film on the rock surface.
Northerly winds at 14–16 km/h provide reasonable airflow across the south-facing boulders, helping to strip surface moisture.
Rhyolite does not absorb water so drying is purely a surface phenomenon — once wind and sun act on it, conditions improve quickly.
Over 100mm of rain fell in the past 28 days with a particularly heavy spell mid-April, keeping the surrounding hillside saturated and contributing ambient moisture.
Cloud cover is forecast at 70–98% through the middle of the day, significantly reducing direct solar radiation on the rock.
Recommendations
3
- Wait until early-to-mid afternoon (after 13:00) to allow maximum drying time, then visually and physically check rock surfaces before climbing.
- Focus on the most exposed, south-facing problems on open walls first — avoid recessed or overhanging features with horizontal breaks where seepage may linger.
- Bring a towel or chalk bag and test friction on lower holds before committing to anything committing or high — if the rock feels glassy or greasy, back off and wait.
Do Not Climb
45%
4 days ago
Today has seen 2.3mm of rain with very high humidity (89%), and the preceding two days also brought light rain — the rock is likely damp right now. Although rhyolite doesn't suffer structural damage when wet, friction will be significantly compromised on these steep boulder problems.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means conditions at the boulders may differ from the road — the higher altitude (300m) and north wind today will slow drying despite the south aspect.
- The stratified formations at Wavelength can channel and hold seepage in horizontal breaks and overlaps, meaning some problems stay damp longer than open faces even after light rain.
- South-facing aspect is helpful but today's northerly wind direction means the boulders are somewhat sheltered from the breeze, reducing effective surface drying.
- The sustained wet spell from mid-April (over 100mm in 28 days) means the surrounding ground and moss are saturated, contributing to ambient moisture around the base of problems.
Warnings
2
- Today's wet surfaces on steep rhyolite will be extremely slippery — a fall from a highball problem on greasy rock could result in serious injury.
- The uphill approach on saturated ground will be slippery; take care on the path.
Reasoning
With 2.3mm of rain today on top of 2.0mm yesterday and 2.1mm the day before, and humidity at 89%, the rock surface is almost certainly damp right now.
Despite the south aspect, today's northerly wind and high humidity provide minimal drying potential; the rock has had zero consecutive dry days to begin surface drying.
Rhyolite is non-porous and structurally unaffected by moisture, so hold breakage and rock damage are not concerns here.
Early May in Snowdonia is transitional — days are lengthening and solar angles are improving, but the recent prolonged wet spell and cool temperatures (~13°C) mean drying is slower than peak summer.
Contributing Factors
6
2.3mm today following 2.0mm and 2.1mm on the previous two days means the rock has been repeatedly wetted with no dry window.
Humidity at 89% severely limits evaporative drying even on surfaces that receive sun.
The south aspect receives good solar radiation in May, which will help once rain stops and skies clear.
Rhyolite does not absorb water, so once rain ceases and a drying window opens, surface moisture will clear relatively quickly.
The south-facing boulders are somewhat sheltered from today's northerly wind, reducing wind-assisted drying.
Over 100mm of rain in the last 28 days means the hillside, turf, and moss around the boulders are thoroughly saturated, maintaining ambient moisture.
Recommendations
3
- Wait for tomorrow at the earliest — the forecast shows a dry day with dropping humidity, which should allow the rhyolite surfaces to begin drying.
- If visiting tomorrow, check holds carefully for residual dampness in horizontal breaks and seepage lines before committing to problems.
- Consider the roadside boulders lower in the Pass as an alternative — lower altitude and more wind-exposed surfaces may dry faster.
Marginal — Assess Conditions
55%
4 days ago
Light rain today (2.3mm) on top of showers over the past two days means the rock is currently damp, but rhyolite at this south-facing venue dries quickly in favourable conditions. A dry spell tomorrow with moderate wind should allow surface moisture to clear, but high humidity (88% today) and northerly wind reducing solar benefit mean on-site assessment is essential before climbing.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means conditions at the boulders can differ significantly from the road — higher altitude (300m) keeps temperatures cooler and humidity can linger in the cwm above the CC hut.
- The stratified rhyolite formations can hold seepage in horizontal breaks and overlapping layers even when main faces appear dry — check slopers and horizontal cracks carefully.
- South-facing aspect is a major asset, but today's northerly wind direction means the boulders are somewhat sheltered from the breeze, reducing drying efficiency compared to the prevailing southwesterlies.
- The venue saw very heavy cumulative rainfall mid-April (over 80mm between Apr 9–17), though a strong dry spell from Apr 21–30 would have fully reset conditions before the recent return of showers.
Warnings
2
- Rock will be slippery today due to surface moisture from ongoing light rain — friction-dependent moves on rhyolite slopers carry genuine fall risk.
- Do not rely on the rock appearing dry from a distance; rhyolite can look dry while retaining a thin moisture film that dramatically reduces friction.
Reasoning
Light but repeated precipitation over the last three days (2.1mm, 2.0mm, 2.3mm today) means surface moisture is present, though total accumulation is modest at around 6.4mm in the past week.
The south-facing aspect and partial wind exposure normally promote rapid drying on rhyolite, but today's northerly wind direction, high humidity (88%), and overcast conditions significantly slow evaporation — expect residual dampness on sheltered faces and in horizontal breaks.
Rhyolite is non-porous and does not suffer structural weakening when wet; there is no hold-breakage concern, and the primary risk is reduced friction on damp surfaces.
Early May in Snowdonia brings lengthening days and increasing solar angle which aid drying, but spring weather remains changeable and mountain humidity can be persistent at 300m altitude.
Contributing Factors
7
Three consecutive days of light rain (2.1mm, 2.0mm, 2.3mm) mean the rock surface has been repeatedly wetted and has had no full dry day to recover.
Humidity at 88% today severely limits evaporation rates, meaning surface moisture will linger much longer than usual on the rock.
The southerly aspect maximises solar exposure during the lengthening spring days, which is the primary drying mechanism for non-porous rhyolite.
North wind at 15 km/h provides limited drying benefit to south-facing rock that is somewhat sheltered from this direction.
Rhyolite does not absorb water, so only surface moisture needs to evaporate — no extended internal drying period is required.
Zero precipitation forecast for May 4 should allow a full day of drying, significantly improving conditions by afternoon.
Nine consecutive dry days from Apr 21–30 (with low humidity and warm temps up to 20°C) fully dried out the rock before the recent showers, so deep seepage from the heavy mid-April rains is not a concern.
Recommendations
3
- Wait until tomorrow afternoon (May 4) when a full dry day with moderate wind should clear surface moisture — assess on arrival by touching key holds before committing to problems.
- Avoid slopers and friction-dependent problems today; if you do visit, stick to steep overhanging lines where seepage is less likely and friction is less critical.
- Check horizontal breaks and stratified ledges carefully for trapped moisture, as these features on the Wavelength boulders can hold water longer than vertical faces.
Do Not Climb
45%
4 days ago
Today has seen 2.1mm of rain with very high humidity (87%), following light rain on the previous two days — the rock is likely damp on the surface right now. While rhyolite dries quickly, the current conditions with low wind (13 km/h from the north, unfavourable for a south-facing crag) and high humidity mean surfaces are unlikely to be reliably dry today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The south-facing aspect is less helpful today with a northerly wind, meaning the boulders are somewhat sheltered from what little drying breeze there is.
- Wavelength Boulders sit at 300m above the Llanberis Pass and the 15–20 minute uphill approach means conditions can differ from roadside — slightly cooler and more exposed to mountain weather than valley crags.
- The stratified rhyolite formations can trap seepage in horizontal breaks and overlaps, and after the very wet mid-April period (over 50mm in four days, Apr 14–17), some deeper seepage lines may still be active despite the dry spell in late April.
- The long dry spell from Apr 21–30 would have cleared most residual moisture, but the return of rain on May 1–3 (6.2mm over three days with rising humidity) has re-wetted surfaces.
Warnings
2
- Wet rhyolite offers dramatically reduced friction — do not trust footholds that feel secure when dry; a slip on a boulder problem can result in a ground fall.
- Three consecutive days of light rain mean even apparently dry-looking surfaces may have a moisture film — test friction before pulling on.
Reasoning
The rock surface is very likely damp today given 2.1mm of rain with 87% humidity and only 13 km/h of northerly wind offering minimal drying on this south-facing venue.
Despite rhyolite's fast-drying nature, the combination of three consecutive days of light rain (May 1–3, totalling 6.2mm), high humidity, and a light northerly wind on a south-facing crag means effective drying has been minimal today.
Rhyolite is non-porous and does not suffer structural damage from moisture — the risk here is purely friction loss on damp surfaces, which is significant for bouldering where falls are common.
Early May in Snowdonia is transitional — days are lengthening and temperatures are mild (~13°C), but the return of Atlantic moisture after the late-April dry spell is typical of spring's unpredictability at this altitude.
Contributing Factors
6
Light rain today (2.1mm) following 2.0mm yesterday and 2.1mm on May 1 means the rock has had no opportunity to fully dry.
Humidity at 87% today severely inhibits evaporation, keeping surfaces damp even where rain hasn't directly fallen.
Light northerly wind at 13 km/h provides minimal drying benefit to these south-facing boulders, which are somewhat sheltered from the north.
Non-porous rhyolite sheds water quickly and only needs hours of favourable conditions to dry, meaning a sunny afternoon break could improve things rapidly.
The excellent 9-day dry spell from Apr 21–30 would have cleared deep seepage from mid-April's heavy rain, so current dampness is likely superficial.
At 300m, temperatures are slightly lower than valley level, slowing evaporation rates compared to roadside venues in the Pass.
Recommendations
3
- Wait for tomorrow (May 4) which is forecast dry with slightly lower humidity — arrive later in the day to allow morning moisture to clear and visually assess surfaces before committing.
- If you do visit today, test friction carefully on lower, less consequential problems before attempting anything committing — wet rhyolite can be treacherously slippery.
- Consider the excellent dry window forecast for May 6–7 (two consecutive dry days with dropping humidity and moderate wind) as a more reliable session.
Marginal — Assess Conditions
55%
5 days ago
Light rain today (2.8mm) on top of 2.1mm yesterday means the rock surface is currently damp, but rhyolite dries quickly and the south aspect helps. Conditions may improve through the afternoon but cannot be called safe without on-site verification.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The 15–20 minute uphill approach means conditions at the boulders may differ from roadside impressions — the higher altitude (300m) can hold cloud and moisture longer than the valley floor.
- Wavelength Boulders' stratified rhyolite formations can create small ledges and horizontal breaks that trap seepage and surface water, requiring inspection even after short dry spells.
- The south-facing aspect is a significant advantage for drying, especially in May when solar angles are high — afternoon sessions are most likely to find dry rock.
- Some overhanging problems and sheltered faces may have stayed dry through today's light rain and could offer climbable options even if slabs and vertical faces remain damp.
Warnings
2
- Do not climb friction-dependent slab problems today — even a thin moisture film on rhyolite dramatically reduces grip and increases fall risk.
- Check BMC RAD for any active bird nesting restrictions in the Llanberis Pass area before visiting, as peregrine nesting season runs through June.
Reasoning
Today's 2.8mm of rain combined with 83% humidity means rock surfaces are likely damp right now, though the precipitation is light and rhyolite does not absorb water.
The south aspect and moderate wind (17.6 km/h SW) will promote surface drying, but high humidity (83%) is limiting evaporation; a few hours of any afternoon sun could dry exposed faces relatively quickly.
Rhyolite is non-porous and extremely hard — there is no risk of structural damage or hold breakage from the recent moisture.
Early May in Snowdonia is improving but still unpredictable; the preceding dry spell (April 21–30 was largely dry) was beneficial, though the last two days have reintroduced surface moisture.
Contributing Factors
7
2.8mm of rain today with 83% humidity means rock surfaces are currently wet or damp.
Combined 4.9mm over the past two days has interrupted a strong drying period, resetting surface conditions.
The south aspect receives strong solar radiation in May, significantly accelerating surface drying when the sun breaks through.
Rhyolite does not absorb water, so surface moisture evaporates quickly once rain stops and conditions improve.
Humidity at 83% today slows evaporation and may keep the rock surface feeling greasy even without active rain.
Nine essentially dry days (April 21–30) means no deep-seated seepage issues; only fresh surface moisture needs to clear.
Partial wind exposure at 17.6 km/h assists surface drying, though the SW direction is warm and moist.
Recommendations
3
- Wait for any rain to stop and allow at least 2–3 hours of breeze or sun before attempting problems — an afternoon session is most likely to find dry conditions.
- Prioritise steep and overhanging problems which may have stayed dry through today's light rain; avoid slabs and friction-dependent routes until surfaces are confirmed dry.
- Touch-test holds carefully before committing — rhyolite becomes notably slippery when even slightly damp, and the stratified features can hold hidden moisture in horizontal breaks.
Marginal — Assess Conditions
62%
6 days ago
After an excellent dry spell from April 21–30, today's 2.3mm of rain has interrupted conditions. The rock was thoroughly dry before today's shower, and the south-facing aspect with moderate wind should allow surface moisture to clear relatively quickly, but today's precipitation means surfaces 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 15–20 minute uphill approach means conditions at the boulders may differ from the road — the higher altitude (300m) can hold cloud and moisture longer than the Pass floor.
- The stratified rhyolite formations can trap water in horizontal seams and ledges; even after light rain, individual problems with layered features or roofs may weep for hours.
- South-facing aspect is a major advantage here — direct solar radiation through the afternoon accelerates surface drying significantly compared to the shaded north side of the Pass.
- Some lower problems near the base of the hillside may retain moisture longer due to drainage from the slope above, particularly after the very wet mid-April period.
Warnings
2
- Rhyolite becomes very slippery when wet — do not attempt problems if any surface moisture is visible, as friction loss is sudden and severe.
- The forecast turns notably wetter and cooler from tomorrow; today may be the last realistic opportunity for several days.
Reasoning
Today's 2.3mm rain has wet the rock surface, but this follows 10 consecutive dry days (April 21–30) that would have thoroughly dried any residual moisture from the heavy mid-April rains.
The south-facing aspect receives good afternoon sun in early May, and moderate 18 km/h southerly wind aids evaporation — surface moisture from today's light rain could clear within a few hours of the rain stopping, but humidity at 71% slows the process.
Rhyolite is non-porous and extremely hard; there is no risk of structural damage or hold breakage from today's moisture — the concern is purely friction loss on damp surfaces.
Early May in Snowdonia offers lengthening days and improving solar angles, but Atlantic weather systems still bring frequent showers; the transition from a warm dry spell to a cooler, wetter pattern is typical of spring.
Contributing Factors
6
2.3mm of precipitation today has wet rock surfaces, breaking the dry streak and meaning the rock is not guaranteed dry right now.
Ten consecutive dry days (April 21–30) with low humidity and strong winds thoroughly dried the rock before today, so there is no deep-seated residual moisture.
The south aspect receives strong afternoon sun in early May, which will actively dry today's light rain from exposed surfaces relatively quickly.
18 km/h southerly wind aids drying, but 71% humidity partially offsets this, resulting in moderate evaporation rates.
The next five days bring frequent light showers (0.4–2.9mm) and high humidity (80–96%), suggesting conditions will not improve and may worsen.
Rhyolite does not absorb water, so once surface moisture evaporates the rock will offer full friction with no risk of internal dampness.
Recommendations
3
- If rain has stopped and the sun is out, wait 2–3 hours then check exposed south-facing problems first — these will dry fastest.
- Carry a towel and avoid any problems with visible dampness, seepage in horizontal seams, or greasy lichen patches.
- Consider this afternoon as the best window before the wetter, cooler spell arrives from May 2 onwards.
Likely Safe to Climb
90%
9 days ago
Wavelength Boulders should be in excellent condition today. The rock has had over a week of essentially dry weather (only 0.3mm in 7 days), with dropping humidity, strong easterly winds, and good solar exposure on the south-facing aspect — more than sufficient to dry non-porous rhyolite thoroughly.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The south-facing aspect and 300m altitude mean the boulders receive strong solar radiation through the afternoon, and the sustained easterly winds of recent days will have accelerated surface drying considerably.
- The uphill approach and elevated position means good natural drainage — water runs off quickly and doesn't pool around the boulders, unlike roadside venues in the Pass.
- Some of the stratified rhyolite formations can harbour residual moisture in horizontal breaks and overlaps; these sheltered features may still be slightly damp from overnight humidity despite the dry spell.
- The high monthly rainfall total (125mm in 28 days) means seepage from the hillside above could still be active on certain problems, particularly those near drainage lines or with overhanging turf at the top.
Warnings
1
- Conditions deteriorate from May 1st onwards with rain returning; today and tomorrow represent the best window before a wetter spell.
Reasoning
With only 0.3mm of rain in the last 7 days, three consecutive fully dry days, and today's humidity at just 50% with strong 39 km/h easterly winds, the non-porous rhyolite surfaces should be completely dry.
The south-facing aspect has received direct solar heating combined with sustained moderate-to-strong winds from the east and southeast over the past week, providing excellent drying conditions far exceeding what rhyolite requires.
Rhyolite is non-porous and extremely hard — there is no risk of structural weakening or hold breakage from the recent wet period.
Late April conditions are favourable with lengthening days providing extended solar drying time; overnight temperatures have remained above freezing, eliminating freeze-thaw concerns.
Contributing Factors
6
Only 0.3mm of precipitation in the last 7 days with 3 consecutive dry days provides ample drying time for non-porous rhyolite.
Current humidity of 50% with a clear downward trend from the 80s earlier in the week means rock surfaces are not rehydrating from atmospheric moisture.
Today's 39 km/h easterly winds and several preceding days of 20–35 km/h winds provide excellent evaporative drying across the partially exposed site.
The south aspect maximises solar heating through the day in late April, accelerating surface evaporation significantly.
125mm over 28 days is substantial, but this is largely irrelevant for non-porous rock given the subsequent week-long dry spell; however, hillside seepage is possible on isolated problems.
Overnight humidity rose to the low 80s before dropping sharply, which could leave very light condensation in sheltered spots but this will evaporate quickly in today's conditions.
Recommendations
3
- Conditions are excellent — head up and enjoy the friction; the strong easterly wind will keep temps comfortable and rock dry.
- Check sheltered horizontal breaks and any problems near drainage lines from the hillside above, as localised seepage from the high monthly rainfall total may persist.
- Bring layers for the approach and for rests between problems — 300m altitude with 39 km/h winds will feel cool despite the 16°C forecast.
Climbing Outlook