Climbing Forecast › North Wales — Llanberis Pass › Cyrn Las

NORTH WALES — LLANBERIS PASS · RHYOLITE

Cyrn Las climbing conditions

Poor — wet, too windy or closed

Right now

Temp7°C
Wind37 km/h
Gusts46 km/h
Humidity100%
Rain 48hdry
Last rainNone recent

Assessment

0.5mm rain forecast
Wind 41 km/h, gusts 54 km/h — too windy
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 forecastWind 41 km/h, gusts 54 km/h — too windyHumidity 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
Caution
Temp8°C
Raindry
Wind21 km/h
Gusts35 km/h
Humidity82%
Drying — 18h since rain
  • 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 Cyrn Las

A serious 150m rhyolite mountain crag hidden high in Cwm Glas Mawr on the south side of the Llanberis Pass — remote in feel despite its position above the road. Cold, north-facing, and slow to come into condition, Cyrn Las needs a proper dry spell. Main Wall (HS 4b, 140m) is widely regarded as the finest mountaineering route at its grade in Wales, zig-zagging up the left side of the cliff on immaculate rock in a memorable atmosphere. The Grooves (E1 5b) and Skyline (VS 4c) are the other must-do lines. Steep 45–60 minute walk-in from the pass. Best kept for a settled forecast after the sunnier Pass crags have already dried.

Region
North Wales — Llanberis Pass
Rock type
Rhyolite
Aspect
north-facing
Altitude
550m
Exposure
high
Seepage
high

Other crags in this region

Carreg WastadClogwyn y GrochanCraig DduCromlech BouldersDinas CromlechDinas Mot