Right now

Temp7°C

Wind37 km/h

Gusts46 km/h

Humidity100%

Rain 48hdry

Last rainNone recent

Assessment

0.5mm rain forecast

Windy — 41 km/h, gusts 54 km/h

Humidity 100% — likely fog/cloud

High humidity (100%) — rhyolite friction compromised, particularly for bouldering

Windy — 37 km/h, gusts 46 km/h. Take care on exposed routes

7-day forecast

Scroll through each day — hourly detail is shown inline.

Today Wednesday 16 September

Poor

Temp7°C

Rain0.5mm

Wind41 km/h

Gusts54 km/h

Humidity100%

0.5mm rain forecastWindy — 41 km/h, gusts 54 km/hHumidity 100% — likely fog/cloud

Damp mountain air — upper pitches may stay greasy
Very windy — consider sheltered alternatives

Time °C Rain Wind (km/h) Gust Hum

12:00 7° dry 37 46 100%

15:00 7° dry 45 54 99.94%

18:00 7° 0.3mm 51 60 99.65%

21:00 7° 0.2mm 57 66 99.61%

Thu Thursday 17 September

Poor

Temp6°C

Rain4mm

Wind49 km/h

Gusts61 km/h

Humidity91%

4.4mm rain forecastWind 49 km/h, gusts 61 km/h — too windyHumidity 91% — potential fog

Wet rhyolite is slippery; seepage from grass above can linger
Very windy — consider sheltered alternatives

Time °C Rain Wind (km/h) Gust Hum

06:00 7° dry 48 57 98.95%

09:00 6° dry 47 57 96.22%

12:00 5° dry 49 61 91.27%

15:00 6° 0.3mm 49 61 90.95%

18:00 6° 0.2mm 47 57 92.68%

21:00 6° dry 50 60 94.75%

Fri Friday 18 September

Poor

Temp7°C

Rain9mm

Wind64 km/h

Gusts90 km/h

Humidity97%

8.9mm rain forecastWind 64 km/h, gusts 90 km/h — too windyHumidity 97% — likely fog/cloud

Wet rhyolite is slippery; seepage from grass above can linger
Very windy — consider sheltered alternatives

Time °C Rain Wind (km/h) Gust Hum

06:00 5° dry 39 49 98.78%

09:00 6° dry 45 59 96.21%

12:00 6° 0.6mm 61 82 95.91%

15:00 7° 5mm 67 90 97.98%

18:00 8° 2mm 60 84 98.77%

21:00 9° 1mm 53 77 98.76%

Sat Saturday 19 September

Poor

Temp9°C

Rain9mm

Wind45 km/h

Gusts72 km/h

Humidity93%

9.1mm rain forecastWind 45 km/h, gusts 72 km/h — too windyHumidity 93% — potential fog

Good temperature for mountain rhyolite
Wet rhyolite is slippery; seepage from grass above can linger
Very windy — consider sheltered alternatives

Time °C Rain Wind (km/h) Gust Hum

06:00 9° 1mm 50 74 98%

09:00 9° 1mm 48 74 96.76%

12:00 9° 2mm 46 72 92.83%

15:00 9° 1mm 44 69 92.27%

18:00 9° 0.9mm 42 62 94.36%

21:00 8° dry 41 58 94.41%

Sun Sunday 20 September

Poor

Temp7°C

Rain0.3mm

Wind28 km/h

Gusts47 km/h

Humidity80%

0.3mm rain forecastWindy — 28 km/h, gusts 47 km/h

Breezy — helps drying

Time °C Rain Wind (km/h) Gust Hum

06:00 5° dry 34 48 94.31%

09:00 6° dry 30 48 87.71%

12:00 7° dry 29 47 80.08%

15:00 8° dry 28 46 80.35%

18:00 8° dry 29 41 90.03%

21:00 7° 0.3mm 32 43 95.9%

Mon Monday 21 September

Poor

Temp10°C

Rain3mm

Wind30 km/h

Gusts47 km/h

Humidity94%

3.3mm rain forecastWindy — 30 km/h, gusts 47 km/hHumidity 94% — potential fog

Good temperature for mountain rhyolite
Wet rhyolite is slippery; seepage from grass above can linger
Breezy — helps drying

Time °C Rain Wind (km/h) Gust Hum

06:00 8° 0.5mm 35 48 98.48%

09:00 9° 0.5mm 32 47 97.29%

12:00 10° 0.5mm 30 47 94.54%

15:00 10° 0.4mm 30 46 94.38%

18:00 10° 0.4mm 31 43 97.53%

21:00 9° 0.3mm 30 41 98.42%

Tue Tuesday 22 September

Poor

Temp10°C

Rain4mm

Wind22 km/h

Gusts38 km/h

Humidity91%

3.5mm rain forecastHumidity 91% — potential fog

Good temperature for mountain rhyolite
Wet rhyolite is slippery; seepage from grass above can linger
Breezy — helps drying

Time °C Rain Wind (km/h) Gust Hum

06:00 9° 0.6mm 30 41 98.23%

09:00 9° 0.6mm 28 42 96.17%

12:00 10° 0.7mm 24 38 91.99%

15:00 10° 0.6mm 20 32 89.42%

18:00 9° 0.3mm 20 27 93.8%

21:00 8° dry 21 27 96.41%

Wed Wednesday 23 September

Good

Temp8°C

Raindry

Wind21 km/h

Gusts35 km/h

Humidity82%

Should be dry

Good temperature for mountain rhyolite
Breezy — helps drying

Time °C Rain Wind (km/h) Gust Hum

06:00 6° dry 21 27 97.25%

09:00 7° dry 20 30 88.93%

12:00 8° dry 21 35 81.76%

About Cromlech Boulders

One of the most internationally famous roadside bouldering venues in the world — a scattered field of huge fallen rhyolite/tuff blocs below Dinas Cromlech in the Llanberis Pass. About 300 established problems from Font 3 up to Font 8A+, with iconic circuits on the Roadside and Wavelength boulders. Jerry's Roof (Font 7C+), first climbed by Jerry Moffatt in 1989, remains the standout hard testpiece. Part of Welsh climbing lore since the Joe Brown era — you can literally step out of the car and start on the easier problems. Boulders face multiple directions across the scatter, so sun or shade can always be found. Best in cool, dry conditions: friction on the coarser rhyolite blocs suffers in warm summer sun.

Region: North Wales — Llanberis Pass
Rock type: Rhyolite
Aspect: mixed-facing
Altitude: 380m
Exposure: medium
Seepage: low

Other crags in this region

Carreg Wastad Clogwyn y Grochan Craig Ddu Cyrn Las Dinas Cromlech Dinas Mot