Condition Analysis
AI-powered assessment using site data and 14-day weather history
Despite a few dry days earlier this week, heavy rain on May 3rd (17.1mm) followed by light rain on May 4th and today (May 7th), combined with high average humidity (78%), means the gritstone is unlikely to be fully dry internally. With 11.4mm of rain forecast tomorrow, conditions are set to deteriorate further.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and main crag face S/SW and are well-exposed to wind, giving them above-average drying potential compared to more sheltered gritstone venues — but the recent pattern of repeated light rain has prevented a sustained drying window.
- Lower sections of the Calf boulder and any north-facing facets or recessed features will retain moisture significantly longer than the prominent south-facing walls.
- The 17.1mm deluge on May 3rd at 95% humidity will have deeply saturated the porous gritstone; only ~3 genuinely dry days have followed, interrupted by 0.7mm on the 4th and 0.9mm today.
- Ilkley Moor's 260m altitude means overnight temperatures have dipped near freezing recently (0.5°C on May 6th), slowing overnight drying and raising minor freeze-thaw concerns for saturated rock.
Warnings
2
- Gritstone can appear surface-dry while remaining saturated internally — do not be deceived by a dry-looking surface after only a short drying window.
- The upcoming week's forecast shows repeated rain; climbing on inadequately dried gritstone causes permanent, irreversible damage to holds and routes.
Reasoning
The heavy 17.1mm rain on May 3rd at near-saturation humidity (95%) will have deeply penetrated the gritstone, and the interrupted drying since then — with further light rain on May 4th, today, and high average humidity of 78% — is insufficient to ensure internal drying.
The S/SW aspect and exposed position are favourable, and there were ~2.5 dry days (May 5–6 plus part of today), but moderate winds (13–16 km/h) and humidity averaging 72–76% during those days limit evaporative drying, leaving the rock likely still damp internally after such a heavy soaking.
Gritstone that absorbed 17mm of rain and has not had a sustained 48–72 hour dry window with good conditions is at significant risk of reduced compressive strength and grain loosening under climbing loads.
Early May in Yorkshire at 260m brings cool overnight temperatures and variable weather; the prolonged wet April (43.6mm over 28 days) means background moisture levels in the rock remain elevated heading into this unsettled period.
Contributing Factors
7
17.1mm of rain at 95% humidity will have deeply saturated the porous gritstone, requiring 48–72+ hours of good drying conditions to recover.
Only about 2.5 dry days since the heavy rain, interrupted by 0.7mm on May 4th and 0.9mm today, falling short of the minimum 48–72 hours of genuinely favourable drying needed.
Average humidity over the last 7 days is 78%, significantly limiting evaporative drying potential even on nominally dry days.
The south/south-west facing aspect and exposed moorland position maximise solar radiation and wind-driven drying, making this one of the faster-drying gritstone venues.
43.6mm over the past 28 days means the rock has had persistently elevated internal moisture levels throughout the period.
11.4mm forecast for May 8th will re-saturate any surface drying achieved, resetting the drying clock entirely.
0.9mm of rain accumulating from late this evening will dampen the rock surface and halt any remaining drying progress today.
Recommendations
3
- Do not climb today — the gritstone has not had a sufficient drying window since the heavy May 3rd rain, and light rain is forecast for this evening.
- Avoid climbing for the foreseeable future; the 5-day forecast shows repeated rain with no sustained dry window likely until at least May 13th.
- When conditions do improve, check the base of the Calf boulder and lower crag sections for dampness before committing — if the ground is moist, the rock is still wet internally.
Previous Analyses
Marginal — Assess Conditions
60%
2 days ago
The last significant rain was 17.1mm on May 3rd, followed by a trace 0.7mm on May 4th, giving roughly 2 full dry days by this afternoon. The S/SW aspect and exposed position help drying, but after heavy rain on porous gritstone, two days is borderline — a visual check on arrival is essential before committing to climb.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and main buttresses face S/SW and are fully exposed on the moor, so they benefit from wind and any solar radiation — these will be the first areas to dry.
- Lower sections and north-facing sides of boulders (e.g. the back of the Calf) will hold moisture much longer after the 17mm event on May 3rd.
- The open moorland setting means the ground around the crag base can be used as a drying indicator — if the peat and grass are still squelchy, the rock likely retains internal moisture.
- Ilkley is a popular venue and well-trafficked; local climbers on UKC forums often post current conditions — checking recent logbook entries before visiting is highly recommended.
Warnings
2
- Rain is forecast from May 7th through May 11th, meaning conditions will deteriorate significantly and remain poor for much of the coming week.
- The 17mm rainfall on May 3rd means internal moisture may persist despite a dry-looking surface — do not rely on visual appearance alone.
Reasoning
The 17.1mm deluge on May 3rd would have thoroughly saturated the gritstone, and the subsequent trace rain on May 4th (0.7mm) plus high humidity (84%) delayed meaningful drying until May 5th.
Two dry days with moderate wind (13–16 km/h) and the S/SW aspect provide reasonable surface drying, but temperatures have been cool (9–11°C) and humidity averaging 72–76%, meaning internal moisture likely persists in thicker sections of rock.
After 17mm of rain only two days ago, internal saturation could still be above the threshold where significant strength loss occurs, posing a real risk of hold breakage on gritstone.
Early May in Yorkshire brings variable conditions; while frost risk is low, cool temperatures and moderate humidity slow the drying process compared to summer conditions.
Contributing Factors
6
17.1mm of rain would have deeply saturated the porous gritstone, requiring substantial drying time.
May 5th and 6th have been dry, providing approximately 48 hours of drying time since the last trace rain on May 4th.
The south-facing, exposed moorland position maximises wind drying and available solar radiation, accelerating surface evaporation.
Average temps around 10°C and overnight lows near 2–5°C slow evaporation rates compared to warmer conditions.
Humidity averaging 68–76% over the drying period reduces the vapour pressure gradient and slows drying.
Rain returns May 7th (2mm) and persists through May 11th, meaning today may be the only climbing window before another prolonged wet spell.
Recommendations
3
- Visit the crag this afternoon when humidity is lowest (51–55%) and visually inspect the rock surface and base ground moisture before climbing.
- Prioritise steep or overhanging problems on the Calf's south-facing side, which will have dried fastest; avoid slabs and lower walls.
- If the peat at the base of the crag is still damp or the rock darkens when touched, do not climb — wait for a longer dry spell.
Marginal — Assess Conditions
60%
3 days ago
Heavy rain on May 3rd (17.1mm) followed by light rain on May 4th (0.7mm) means the rock has had less than two full dry days. The S/SW aspect, exposed position, and moderate wind today are helping, but internal moisture is likely still present — a visual and touch check on arrival is essential before committing to climb.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and main buttress face S/SW and are fully exposed to wind, so they dry significantly faster than the sheltered gullies and north-facing side walls that can hold seepage for days longer.
- Cow and Calf sits on open moorland at 260m; boggy ground around the crag base is a reliable indicator of residual moisture in the rock — if the peat and grass are still squelchy, the grit is still damp internally.
- The bouldering circuit includes lower, sheltered problems near the base of the hillside that will retain moisture longer than the prominent upper faces and the top of the Calf boulder.
- The period from mid-April through early May has been persistently unsettled with 42.7mm over 28 days, meaning the gritstone has had limited opportunity to fully dry out at depth between rain events.
Warnings
2
- Heavy rain (17.1mm) fell less than 48 hours ago — the rock may appear surface-dry while remaining dangerously weakened internally; climbing on insufficiently dried gritstone causes permanent hold damage.
- Overnight low of -1.3°C forecast for May 6th could cause freeze-thaw damage if residual internal moisture remains above the critical saturation threshold.
Reasoning
17.1mm fell on May 3rd with a further 0.7mm on May 4th evening, and only ~1.5 dry days have elapsed since — the rock surface may be drying but internal moisture from the heavy rain is very likely still present.
The S/SW aspect and exposed 20 km/h northerly wind today are aiding evaporation, and humidity has dropped to the low 60s this afternoon, but the overnight high humidity (85%) and overcast skies limit drying effectiveness — full drying from 17mm of rain typically requires 48–72+ hours.
Gritstone that absorbed 17mm of rain only ~48 hours ago could still retain significant internal moisture, risking 10–50% compressive strength loss and grain loosening on stressed holds.
Early May temperatures (5–11°C) are modest and overnight lows approaching 0°C on May 6th could cause freeze-thaw stress if residual internal moisture remains; the prolonged unsettled spring has limited cumulative drying.
Contributing Factors
8
17.1mm on May 3rd is classified as heavy rain requiring 48–72+ hours of dry weather for adequate drying of porous gritstone.
An additional 0.7mm fell at 19:00 on May 4th, re-wetting the surface and resetting the drying clock slightly.
Only approximately 30 hours have passed since the last rain, well short of the recommended 48–72 hour minimum after heavy rain.
The south/south-west facing, fully exposed position maximises solar gain and wind drying, making Cow and Calf one of the faster-drying gritstone venues.
A 20 km/h northerly wind and afternoon humidity dropping to 61–65% are actively aiding surface evaporation.
Temperatures of 9–11°C today are adequate for evaporation but not warm enough to drive rapid deep drying.
42.7mm over the past 28 days with frequent small rain events means the rock has had limited opportunity to dry fully at depth between wettings.
No rain is forecast for the next 6 days, meaning conditions will steadily improve from tomorrow onwards.
Recommendations
3
- If visiting today, perform a thorough touch test on multiple faces — press your palm firmly against the rock in shaded areas and at the base; any coolness or darkening indicates residual moisture.
- Prioritise the upper, most exposed south-facing faces of the Calf boulder which will have dried fastest; avoid sheltered lower problems and north-facing walls.
- Consider waiting until tomorrow (May 6th) or the day after for higher confidence, as each additional dry day with low humidity and wind will significantly improve conditions.
Do Not Climb
35%
4 days ago
Heavy rain (17.1mm) fell yesterday (May 3rd) with near-saturated humidity throughout the day, and the rock has had less than 24 hours of drying in poor conditions (overcast, high humidity, light winds). The gritstone will still be significantly wet internally despite any surface improvement this afternoon.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and main buttress faces south/south-west, which helps drying, but today's cloud cover until late afternoon and light morning winds severely limit solar-driven evaporation.
- Seepage lines and horizontal breaks on the Cow buttress tend to hold moisture for days after heavy rain — these areas will be visibly wet and should be avoided entirely.
- The exposed moorland setting normally aids wind-drying, but today's winds are light (under 10 km/h) through the morning, only picking up to ~15 km/h by evening — far less helpful than usual.
- The preceding weeks have been persistently damp (42mm in 28 days with frequent light rain events), meaning background moisture levels in the gritstone were already elevated before yesterday's heavy soaking.
Warnings
2
- Climbing on saturated gritstone causes permanent hold breakage and irreversible erosion — the Cow and Calf's iconic problems are irreplaceable.
- The rock surface may appear to dry this afternoon in the breeze, but the interior will remain saturated — this is the most dangerous scenario for hold failure.
Reasoning
17.1mm of rain fell yesterday in near-saturated conditions (94% humidity, 100% cloud), thoroughly wetting the porous gritstone to depth; with less than 24 hours of poor drying since, the rock will be substantially saturated internally.
Overnight humidity was 95–98% with light winds, providing essentially zero net evaporation; today's afternoon improvement (humidity dropping to ~60%, light breeze, some cloud breaks) offers only a few hours of modest drying — far short of the 48–72 hours needed after heavy rain.
At current saturation levels the gritstone will have lost 10–50% of its compressive strength, making hold breakage a real risk, particularly on well-trafficked problems on the Calf boulder.
Spring conditions are improving but the preceding weeks of intermittent rain have kept background moisture high; overnight frost risk is minimal today but temperatures remain cool, slowing evaporation.
Contributing Factors
6
17.1mm fell on May 3rd — this is a heavy rain event requiring 48–72+ hours of good drying conditions before gritstone is safe to climb.
Less than 24 hours have passed since heavy rain, with overnight conditions (95–98% humidity, light wind, full cloud) providing virtually no evaporative drying.
42mm of rain over the past 28 days with frequent small rain events means the rock's background moisture was already elevated before yesterday's soaking.
Humidity drops to ~60% by late afternoon with clearing skies and a light breeze, beginning some useful surface drying — but this is insufficient to dry 17mm of rain from porous gritstone.
The S/SW aspect and exposed moorland position are favourable for drying, but these advantages are largely negated today by cloud cover and light winds.
Humidity remained above 94% from yesterday evening through this morning, meaning no meaningful drying occurred overnight.
Recommendations
3
- Do not climb today — the gritstone needs at least 48 hours of dry weather with reasonable drying conditions after yesterday's 17mm soaking.
- Check back on Wednesday May 6th at the earliest, by which time the forecast shows two full dry days with lower humidity (62%) and moderate wind.
- If visiting today for a walk or to scope lines, check the base of the crag — if the ground is damp, the rock is certainly still wet internally.
Do Not Climb
95%
4 days ago
Today is clearly unsuitable for climbing at Cow and Calf. Heavy rain today (17.2mm) at very high humidity (94%) means the gritstone will be thoroughly saturated, with no drying opportunity whatsoever.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and surrounding blocks are exposed on open moorland, which normally aids drying, but today's heavy rain and near-saturated air negate this advantage entirely.
- The south/south-west aspect is unhelpful today with NE winds driving moisture onto the main faces and overcast skies limiting solar drying.
- Ilkley's Millstone Grit is notably porous and the recent pattern of intermittent rain (1.5mm on May 2, plus repeated light showers through mid-to-late April) means the rock never fully dried out before today's heavy soaking.
- The popular lower problems on the Calf boulder and surrounding outcrops tend to collect drainage from above and will be among the last areas to dry after a significant wetting event like today.
Warnings
2
- Climbing on saturated Millstone Grit risks catastrophic hold failure — holds that feel solid when dry can snap without warning when wet.
- The rock surface may appear to dry quickly in wind or sun but internal saturation persists far longer — do not be deceived by a dry-looking surface.
Reasoning
With 17.2mm of rain today at 94% humidity, the gritstone is fully saturated to depth; the preceding days included 1.5mm on May 2 and trace rain on April 28, so the rock had not fully dried before this major soaking event.
There has been zero drying today — the NE wind is pushing moisture onto the S/SW faces, humidity is near saturation, and the rain is ongoing; effective drying cannot begin until precipitation stops and humidity drops significantly.
Millstone Grit loses 10–50% of its compressive strength when wet, and with the rock currently at or near full saturation, holds are at serious risk of breakage — climbing now would risk permanent damage to this heavily-used venue.
Early May in Yorkshire brings improving temperatures but spring weather remains unsettled; the April pattern of frequent light-to-moderate rain has kept background moisture levels elevated, compounding today's heavy event.
Contributing Factors
7
17.2mm of rain today is a significant wetting event that will fully saturate the porous Millstone Grit to considerable depth.
Humidity at 94% means virtually no evaporative drying is possible, prolonging saturation.
Zero consecutive dry days means the rock has had no opportunity to begin drying from today's rain, and the preceding days included additional light rain (1.5mm on May 2).
NE winds blow directly onto the S/SW-facing rock surfaces, reducing the normal drying advantage of this aspect.
18.8mm in the last 7 days and 44.2mm over 28 days indicates the rock has been repeatedly wetted without sustained drying periods, keeping background moisture elevated.
Temperatures around 10°C are adequate for drying in principle but irrelevant today given the ongoing rain and saturated air.
The exposed moorland position is an advantage in dry weather but provides no benefit during active precipitation.
Recommendations
3
- Do not climb today — the rock is saturated and climbing would risk permanent hold damage and personal injury.
- Wait for at least 48 hours of dry, breezy weather with humidity below 70% before considering a return.
- Check the ground at the base of the crag before climbing in coming days — if the soil and peat are still visibly damp, the rock almost certainly retains dangerous levels of internal moisture.
Do Not Climb
95%
4 days ago
Today has seen 18.8mm of heavy rain with 93% humidity — the rock is thoroughly saturated and climbing would risk both hold damage and climber safety. Conditions will need at least 48 hours of dry weather before climbing can be considered.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and surrounding blocks have multiple horizontal breaks and cracks that trap water and prolong seepage, meaning even after the surface dries these features can weep for days after heavy rain.
- The S/SW aspect and exposed moorland position are significant advantages for drying, but the easterly wind forecast for tomorrow will not directly ventilate the south-facing surfaces as effectively as a westerly or south-westerly would.
- At 260m on open moorland, the crag benefits from wind exposure but temperatures are slightly cooler than valley-floor sites, and overnight lows near 3–5°C will slow drying considerably.
- The preceding two weeks have been relatively dry (only light, scattered precipitation since April 18), so the rock was not deeply saturated before today's heavy rain — this improves the outlook for mid-week recovery.
Warnings
2
- Climbing on saturated gritstone today risks permanent hold breakage and route damage — Millstone Grit loses up to 50% of its compressive strength when wet.
- The rock surface may appear dry before the interior has dried — do not be deceived by surface appearance alone; check for darkened patches in cracks and at the base.
Reasoning
18.8mm of rain today at 93% humidity means the gritstone is fully saturated throughout, with capillary absorption likely reaching near-maximum levels within the first few hours of rain.
With the rain only falling today and tomorrow forecast at 84% humidity with light 10 km/h easterly winds, meaningful drying of the south-facing rock will be slow — at least 48 hours of dry weather with moderate wind and lower humidity are needed before the interior approaches safe moisture levels.
Millstone Grit loses 10–50% of its compressive strength when wet, and today's thorough soaking means holds are at significantly elevated risk of breakage; climbing today or tomorrow would risk permanent route damage.
Spring conditions in late April/early May are generally improving, but overnight lows near freezing (April 24 saw -0.7°C) are still possible at 260m and could compound moisture damage through freeze-thaw if the rock remains wet overnight.
Contributing Factors
7
18.8mm of rain is a significant soaking event that will saturate the gritstone to depth, requiring extended drying time.
93% humidity today effectively prevents any meaningful evaporative drying from occurring.
1.5mm on May 2nd and scattered light rain over the previous fortnight means the rock was not fully dry before today's deluge.
South and south-west facing rock receives good solar radiation which will help once skies clear, accelerating surface drying from tomorrow onwards.
The open moorland setting allows wind to strip moisture from the rock surface effectively, though tomorrow's light easterly winds will be less helpful for south-facing surfaces.
From May 5th onwards, humidity drops significantly (to 52% by May 7th) with negligible precipitation, creating good drying conditions.
Average temperatures around 10–13°C are adequate but not exceptional for drying; overnight lows around 3–5°C slow the process.
Recommendations
3
- Do not climb today — the rock is thoroughly soaked and unsafe; use the time to visit the nearby café and plan for mid-week sessions.
- Wait until at least May 6th before considering a visit, and perform a touch test on the rock and check that the ground at the base of the crag is sandy-dry before climbing.
- If visiting mid-week, prioritise upper sections and overhanging faces on the Calf boulder which will dry fastest; avoid lower slabs and any routes with visible seepage.
Do Not Climb
95%
4 days ago
Today has seen 20.2mm of heavy rain with 94% humidity — the gritstone at Cow and Calf will be thoroughly saturated and is completely unsuitable for climbing. With the preceding wet period (21.8mm in the last 7 days) the rock will have had no chance to dry out internally, and conditions today are as bad as they get.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and surrounding blocks are exposed to wind from most directions, which will aid drying once rain stops, but the sheer volume of today's rainfall means even exposed faces will be thoroughly soaked.
- Seepage lines on the main Cow buttress and around the base of the Calf boulder can persist for days after heavy rain, especially where water tracks down from the moorland above.
- The S/SW aspect is favourable for solar drying but recent easterly winds mean airflow hasn't been hitting the main faces optimally; tomorrow's light easterly wind won't help the south-facing rock dry quickly.
- The moorland setting means water drains across and down through the gritstone from the saturated peat above, prolonging internal moisture well beyond what surface appearances suggest.
Warnings
3
- Climbing on saturated gritstone risks permanent hold breakage and irreversible route damage at one of Yorkshire's most important venues.
- The rock surface may appear dry before the interior has dried — do not trust surface appearance alone after this volume of rain.
- Overnight temperatures near freezing (forecast min -0.7°C recently, and 3-4°C this week) combined with saturated rock create freeze-thaw damage risk.
Reasoning
With 20.2mm of rain today at 94% humidity, on top of 1.5mm yesterday and a generally unsettled preceding fortnight, the gritstone will be fully saturated to depth — likely near the ~87-90% saturation ceiling.
Drying has not yet begun; the rain is still falling or only just stopping today, and with 94% humidity and only 10°C there is negligible evaporative potential — meaningful drying cannot start until tomorrow at the earliest.
At full saturation the gritstone faces 10-50% compressive strength loss; climbing today or in the immediate aftermath would risk hold breakage and permanent damage to this heavily-used and irreplaceable venue.
Spring conditions in late April/early May are improving but today's heavy shower demonstrates the volatility of the season; overnight lows near or just below freezing in recent weeks add a minor cumulative freeze-thaw concern for recently wetted rock.
Contributing Factors
8
20.2mm of rain today is well above the 10mm 'heavy rain' threshold, requiring 48-72+ hours of dry weather before climbing.
Humidity at 94% means essentially zero net evaporation is occurring, so no drying progress can be made today.
21.8mm in the last 7 days and 47.2mm over the last 28 days mean the rock had limited opportunity to fully dry before today's soaking.
The south and south-west facing aspect will receive good solar radiation to aid drying once conditions improve.
The open moorland setting allows wind to reach the rock from most directions, significantly accelerating drying once humidity drops.
Only 0.6mm of precipitation is forecast over the next 6 days, providing a good drying window if it materialises.
Temperatures around 10-13°C are adequate but not exceptional for evaporative drying; not cold enough to halt drying but not warm enough to accelerate it significantly.
Water draining through saturated peat moorland above the crag will continue to feed moisture into the rock from behind for an extended period after rain stops.
Recommendations
3
- Do not climb today — the rock is fully saturated and structurally compromised; wait for a sustained dry period.
- Allow a minimum of 48-72 hours of dry weather from tomorrow before considering a visit; realistically Tuesday 6th May at the earliest for an on-site assessment.
- Check the base of the crag and lower sections of the Calf boulder for dampness before committing — if the ground is moist or the rock base feels cool and damp, walk away.
Do Not Climb
45%
5 days ago
Today has seen 1.2mm of rain, breaking a good dry spell, and tomorrow brings a heavy 23mm downpour — conditions are deteriorating rapidly. While the preceding dry spell (April 21–May 1) would have dried the rock well, today's rain and the imminent heavy forecast make climbing inadvisable from today onwards.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and surrounding blocks have varied aspects; south/south-west faces will have benefited most from the preceding dry spell but today's rain re-wets exposed surfaces.
- The open moorland setting at Cow and Calf means the 23mm forecast for tomorrow will hit all faces with little shelter, and drainage from the moor above can cause prolonged seepage on lower sections.
- East winds over the last week would not have directly aided drying on the S/SW faces as effectively as a westerly would, though the long dry spell compensated.
- At 260m altitude, overnight temperatures near or below freezing (e.g. -0.7°C on April 24) during the recent dry spell may have caused minor freeze-thaw stress on any residually damp sections.
Warnings
2
- A 23mm deluge is forecast for tomorrow (May 3) — avoid the crag entirely; wet gritstone loses up to 50% of its compressive strength.
- The coming week has repeated rain events (May 3, 5, 6) totalling nearly 38mm — do not assume the rock is dry between showers, as internal moisture will persist even if the surface appears dry.
Reasoning
The rock likely entered today in good dry condition after 10+ consecutive dry days (April 21–May 1), but today's 1.2mm of rain has begun re-wetting the surface, and with 77% humidity, drying today will be limited.
The extended dry spell from April 21 to May 1 with moderate temperatures (11–21°C) and decent wind would have dried the grit thoroughly, but today's rain resets the clock and tomorrow's 23mm deluge will fully saturate the rock.
The gritstone was likely in good structural condition after the long dry spell, but the incoming heavy rain (23mm tomorrow, plus further rain on the 5th and 6th) poses significant re-saturation and strength-loss risk for days to come.
Spring conditions in late April/early May are improving but remain unpredictable; the forecast wet spell is typical of spring weather in Yorkshire and will require substantial drying time afterwards.
Contributing Factors
6
1.2mm of rain today has broken the dry spell and begun re-wetting the gritstone surface, with 77% humidity limiting evaporation.
A substantial 23mm of rain forecast for May 3 will fully saturate the porous gritstone, requiring 48–72+ hours of dry weather to recover.
Over 10 consecutive dry days (April 21–May 1) with moderate temperatures thoroughly dried the rock before today's deterioration.
Further rain on May 5 (5.3mm) and May 6 (9.4mm) means the rock will not get the sustained dry period needed to recover after tomorrow's soaking.
The exposed moorland position and south/south-west aspect maximise solar gain and wind exposure, which will help once dry weather eventually returns.
Humidity of 89% tomorrow and 82–84% on the 5th and 6th will severely impede drying between rain events.
Recommendations
3
- Do not climb today or tomorrow — the rock is being re-wetted and a major soaking is imminent.
- The earliest realistic window is May 7–8 after the forecast clears, but only if the rain on the 5th and 6th is as predicted — visually inspect the rock and check the base of the crag for dampness before committing.
- Consider alternative non-porous venues (e.g. limestone or volcanic rock) during this wet spell if you need a climbing fix.
Likely Safe to Climb
85%
6 days ago
Ilkley Cow and Calf has had an excellent drying window — essentially dry since April 21st with only a trace of rain (0.1mm on April 20th and 28th), warm temperatures reaching nearly 18–20°C, and moderate winds. The south/south-west aspect and exposed position mean conditions should be genuinely dry today.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and main buttresses face S/SW, receiving strong afternoon sun which has been effective during this extended dry spell.
- The exposed moorland setting means the persistent easterly winds over the last week have provided good airflow across the rock faces, though east winds are less directly helpful for the S/SW-facing rock.
- The heavy rain on April 11th (10.1mm) followed by intermittent showers through April 18th would normally require extended drying, but the subsequent 12+ days of near-zero precipitation provides ample time.
- Lower sections and any north-facing nooks around the base of the Calf boulder may still hold residual dampness from the wetter mid-April period — check these areas before committing.
Warnings
1
- Heavy rain forecast for May 3rd (9.1mm) will reset conditions — do not assume this weekend will be climbable.
Reasoning
With only 0.1mm of precipitation in the last 10 days and effectively no rain since April 20th, the rock should be thoroughly dried through — well beyond the 48–72 hour guideline even for heavy rain.
The S/SW aspect has received strong spring solar radiation, temperatures have been warm (15–20°C), and moderate winds have aided evaporation over a sustained 10+ day drying period, which is more than adequate.
Structural risk is very low given the extended dry period; internal moisture from mid-April rains should have fully evaporated by now, and there is no freeze-thaw concern with overnight lows well above 0°C recently.
Late April/early May is an improving season for gritstone climbing — longer days, stronger sun angles, and warmer temperatures all support good conditions, though spring showers can arrive quickly.
Contributing Factors
7
Effectively 10+ consecutive dry days (only 0.1mm trace rain) since the last meaningful precipitation on April 18th, far exceeding the 48–72 hour guideline.
Temperatures reaching 15–20°C over the last week with today forecast at 20.5°C, providing strong evaporative potential.
South and south-west facing rock receives excellent solar radiation in late April/May, maximising surface and subsurface drying.
The exposed moorland setting ensures good airflow across the rock, significantly aiding drying even when winds have been moderate at 15–28 km/h.
Average humidity of 69% over the last week is reasonable for spring and does not impede drying significantly.
The heavier rain in mid-April (10.1mm on April 11th plus surrounding days totalling ~20mm) would have deeply saturated the rock, but the subsequent 12+ dry days have allowed thorough drying.
Significant rain (9.1mm) is forecast for May 3rd which will end this dry window and require another full drying cycle.
Recommendations
3
- Today (May 1st) and tomorrow (May 2nd) represent the best window before rain arrives on May 3rd — make the most of it.
- Check the base of the Calf boulder and any sheltered or north-facing sections for residual dampness before climbing, particularly in shaded cracks.
- Be aware that conditions will deteriorate significantly from May 3rd onwards — plan accordingly if visiting this weekend.
Likely Safe to Climb
85%
9 days ago
The rock at Cow and Calf should be dry today. The last meaningful rain was 1.5mm on April 18th — over 10 days ago — followed by an extended dry spell with good temperatures and moderate wind, providing ample drying time for this exposed, south-facing gritstone venue.
Based on weather conditions only — does not cover bird nesting restrictions or other access issues.
- The Calf boulder and main buttress face S/SW and are fully exposed to wind and sun, meaning they benefit from excellent drying conditions and should be thoroughly dry after 10+ days without significant rain.
- Lower sections and north-facing aspects of some boulders (e.g. the back of the Calf) may retain slightly more moisture from the overnight high humidity and could feel cooler to the touch — assess these areas individually.
- The 31.4mm of rain over the past 28 days represents a moderately wet April, but the bulk fell before April 18th, and the subsequent 10+ dry days are well in excess of the 48–72 hour guideline even for heavy rain on gritstone.
- The easterly wind today (30.6 km/h) is blowing across the moor rather than directly onto the main S/SW faces, but at this exposed altitude it still provides excellent air circulation for maintaining dry conditions.
Reasoning
The last significant precipitation was 1.5mm on April 18th, over 10 days ago, with only a trivial 0.1mm trace on April 20th and 28th — the rock interior should be fully dry after this extended dry spell.
Over 10 consecutive essentially-dry days with temperatures reaching 15–18°C, moderate winds, and the S/SW exposed aspect mean drying has been thorough and complete, far exceeding the 48–72 hour guideline.
With the rock fully dried out over an extended period, structural risk from grain loosening or hold breakage is minimal — the gritstone should be at full compressive strength.
Late April offers improving temperatures and lengthening days; the overnight frost on April 24th (-0.7°C) is not a concern given the rock was already dry, and no freeze-thaw risk exists with the current dry internal state.
Contributing Factors
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Over 10 days since any meaningful rain (1.5mm on April 18th), with only trace amounts since, far exceeding the 48–72 hour drying guideline for gritstone.
The S/SW aspect and exposed moorland position maximise solar radiation and wind exposure, providing optimal drying conditions.
Temperatures of 10–18°C over the drying period with consistent moderate winds (13–27 km/h) have driven thorough evaporation.
Humidity reached 92% overnight but is dropping today with 65% daytime humidity and 30.6 km/h wind, so surface condensation will evaporate quickly.
April total of 31.4mm is moderate but was concentrated in the first half of the month, with the prolonged dry spell since fully compensating.
Recommendations
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- Conditions are good for climbing — enjoy the gritstone in excellent spring conditions.
- Check the base of any north-facing or sheltered boulder faces for residual dampness, particularly if climbing early in the morning before overnight humidity dissipates.
- Use minimal chalk and brush holds with a soft boar's hair brush after your session, as per Yorkshire gritstone ethics.
Climbing Outlook