Gallt yr Ogof weather forecast.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Around 100% early, falling to around 20% later.

A wild day on Gallt yr Ogof: summit wind broadly 15-40 mph, with gusts 45-55 mph around midday (gale-force winds). Thunderstorms are a significant hazard from late afternoon into the evening. Exposed summits and ridges are a poor choice while storms are nearby. High spate risk based on forecast rainfall. Burns and unbridged crossings may become difficult or impassable. Most likely from around 11:00 until around 19:00. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 1100–1400 m in the morning, then around 3000–3300 m around midday and 400–700 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view from early morning into the afternoon. A persistently wet day is possible, with around 10-20 mm indicated; local totals could vary considerably.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Cloudier around midday at about 0%; around 33% early and 40% later.

A grey, cloudy day on Gallt yr Ogof: summit wind broadly 15-35 mph, with gusts 40-50 mph during the evening (gale-force winds). Thunderstorms are a significant hazard from the morning into the afternoon. Exposed summits and ridges are a poor choice while storms are nearby. The ground is likely to be saturated after recent rain. Expect boggy paths and rapid runoff if more rain arrives. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 600–900 m in the morning, lowering to 500–800 m around midday and 400–700 m by late afternoon. The top is likely to drift in and out of cloud, with the best chance of a view during the evening. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. Some rain is likely, with around 2-5 mm indicated; timing and local totals remain uncertain. Confidence moderate (Summit wind could be roughly 20-38 mph, which changes how difficult exposed walking may feel) - the summit peak could reasonably be 20-38 mph, so treat the headline as mid-range.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

A grey, cloudy day on Gallt yr Ogof: summit wind broadly 15-30 mph, with gusts 30-40 mph early in the morning (strong winds). A meaningful thunderstorm risk is indicated from around midday into the evening. Avoid committing to exposed ridges if storms begin to build. The ground is likely to be wet after recent rain. Much calmer lower down - generally 0-10 mph in the valley, rising towards the tops. Cloud base mostly around 400–700 m through daylight. Expect the top to stay in cloud for most or all of daylight, with no dependable break. Cloud is likely to hang lowest on southwestern slopes; the northeastern side should see somewhat higher bases and better breaks. Some rain is likely, with around 5-10 mm indicated; timing and local totals remain uncertain. Confidence moderate (Summit wind could be roughly 20-36 mph, which changes how difficult exposed walking may feel) - the summit peak could reasonably be 20-36 mph, so treat the headline as mid-range.

Forecast confidence: Thunderstorm timing is inherently uncertain and may shift by several hours.

Cloud-free timing: Best around midday at about 100%; around 67% early and 80% later.

A wild day on Gallt yr Ogof: summit wind broadly 20-40 mph, with gusts 45-55 mph during the evening (gale-force winds). Thunderstorms are a significant hazard from early morning into the evening. Exposed summits and ridges are a poor choice while storms are nearby. The ground is likely to be wet after recent rain. Much calmer lower down - generally 10-20 mph in the valley, rising towards the tops. Cloud is likely to hang lowest on southwestern slopes; the northeastern side should see somewhat higher bases and better breaks. Some rain is likely, with up to around 2 mm indicated; timing and local totals remain uncertain. Confidence moderate (Summit wind could be roughly 21-43 mph, which changes how difficult exposed walking may feel) - the summit peak could reasonably be 21-43 mph, so treat the headline as mid-range.

Forecast confidence: Summit wind could be roughly 39-61 mph, which changes how difficult exposed walking may feel.

Cloud-free timing: Cloudy early, clearing later.

A wild day on Gallt yr Ogof: summit wind broadly 35-50 mph, with gusts 60-70 mph early in the morning (storm-force winds). Much calmer lower down - generally 15-25 mph in the valley, rising towards the tops. Cloud base around 600–900 m in the morning, lifting to 1100–1400 m around midday and 1700–2000 m by late afternoon. Summit cloud should lift later, bringing a better chance of clear views. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. Some rain is likely, with around 2-5 mm indicated; timing and local totals remain uncertain. Cold on top: air temperature broadly 6 to 10°C, feeling around 0 to 4°C in the wind - wrap up. Low confidence (Summit wind could be roughly 39-61 mph, which changes how difficult exposed walking may feel) - the summit peak could be anywhere from 39 to 61 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 confidence: Rain is possible, but forecast models differ by about 14 hours on when it arrives.

Cloud-free timing: Around 67% early, improving to around 100% later.

A mixed day on Gallt yr Ogof: summit wind broadly 20-35 mph, with gusts 35-45 mph around midday (gale-force winds). Much calmer lower down - generally 10-20 mph in the valley, rising towards the tops. Any cloud sits well above the tops (base 1200-1700 m) - clear summits. Cloud is likely to hang lowest on western slopes; the eastern side should see somewhat higher bases and better breaks. Some rain is likely, with up to around 2 mm indicated; timing and local totals remain uncertain. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 23-34 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.