A grey, cloudy day on Craig Cwm Silyn: summit wind broadly 15-35 mph, with gusts 35-45 mph early in the morning (gale-force winds). Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base 600-1100 m - the top is likely to drift in and out of cloud, with the best chance of a view from late afternoon into the evening. Cloud will be lowest on the W slopes, down to about 500-800 m; the E side should be clearer, lifting to around 700-1000 m. Little or no rain expected.
Craig Cwm Silyn weather forecast.
734 m summit forecast for wind, cloud, rain and temperature. Updated from the Thursday 6 August 2026 model run.
Seven-day Craig Cwm Silyn forecast.
Conditions can change quickly with height. Use the day-by-day summit detail below, then check again close to departure.
A fine day on Craig Cwm Silyn: summit wind broadly 5-20 mph, with gusts 15-25 mph around midday (fresh and blowy). Little or no rain expected.
A fine day on Craig Cwm Silyn: summit wind broadly 10-25 mph, with gusts 25-35 mph during the evening (fresh and blowy). Any cloud sits well above the tops (base 700-1300 m) - clear summits. Little or no rain expected. Bright spells with UV up to 6 - sunscreen on exposed skin. Confidence moderate (ensemble members show a moderate spread) - the summit peak could reasonably be 16-24 mph, so treat the headline as mid-range. Cloud base is the least certain part of this - the models are only moderately agreed, so it could sit a couple of hundred metres either way.
A fine day on Craig Cwm Silyn: summit wind broadly 5-25 mph, with gusts 20-30 mph early in the morning (fresh and blowy). Much calmer lower down - generally 0-10 mph in the valley, rising towards the tops. Any cloud sits well above the tops (base 1100-3100 m) - clear summits. Little or no rain expected. Bright spells with UV up to 6 - sunscreen on exposed skin. Low confidence (ensemble members are widely spread) - the summit peak could be anywhere from 10 to 26 mph; check again nearer the time. Treat the cloud base with caution - the models disagree on humidity, so it could be well above or below the figure given.
A fine day on Craig Cwm Silyn: summit wind broadly 5-15 mph, with gusts 5-15 mph early in the morning (a moderate breeze). Little or no rain expected. Bright spells with UV up to 6 - sunscreen on exposed skin. Low confidence (ensemble members are widely spread) - the summit peak could be anywhere from 5 to 13 mph; check again nearer the time. Cloud base is the least certain part of this - the models are only moderately agreed, so it could sit a couple of hundred metres either way.
A mixed day on Craig Cwm Silyn: summit wind broadly 10-25 mph, with gusts 25-35 mph early in the morning (strong winds). Much calmer lower down - generally 0-10 mph in the valley, rising towards the tops. Little or no rain expected. Bright spells with UV up to 6 - sunscreen on exposed skin. Low confidence (ensemble members are widely spread) - the summit peak could be anywhere from 10 to 33 mph; check again nearer the time. Cloud base is the least certain part of this - the models are only moderately agreed, so it could sit a couple of hundred metres either way.
A mixed day on Craig Cwm Silyn: summit wind broadly 20-35 mph, with gusts 35-45 mph early in the morning (strong winds). Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base 500-1000 m - the top is likely to drift in and out of cloud, with the best chance of a view from early morning into the afternoon. Little or no rain expected. Low confidence (ensemble members are widely spread) - the summit peak could be anywhere from 20 to 43 mph; check again nearer the time. Cloud base is the least certain part of this - the models are only moderately agreed, so it could sit a couple of hundred metres either way.
Forecast run: 2026-08-06
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Mountain weather can differ sharply from conditions in the valley. Check official warnings, carry appropriate navigation and clothing, and be ready to change the plan.