Pen yr Helgi Du weather forecast.

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

Cloud-free timing: Around 100% early, falling to around 40% later.

A wild day on Pen yr Helgi Du: summit wind broadly 15-35 mph, with gusts 35-45 mph during the morning (gale-force winds). Thunderstorms are forecast from the morning into the evening. Avoid exposed summits and ridges during the risk period. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 08:00 until around 22:00. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud is likely to hang lowest on southeastern slopes; the northwestern side should see somewhat higher bases and better breaks. 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: Clear early, clouding up later.

A rough, clagged-in day on Pen yr Helgi Du: summit wind broadly 10-30 mph, with gusts 35-45 mph during the morning (strong winds). A meaningful thunderstorm risk is indicated from early morning into the evening. Avoid committing to exposed ridges if storms begin to build. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 09:00 until around 03:00 the following day. Much calmer lower down - generally 5-15 mph in the valley, rising towards the tops. Cloud base around 1100–1400 m in the morning, lowering to 700–1000 m around midday and 500–800 m by late afternoon. The summit should be clear early, with cloud building around midday. A persistently wet day is possible, with around 10-20 mm indicated; local totals could vary considerably. Confidence moderate (Summit wind could be roughly 19-35 mph, which changes how difficult exposed walking may feel) - the summit peak could reasonably be 19-35 mph, so treat the headline as mid-range.

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

Cloud-free timing: Around 0% early, improving to around 40% later.

A rough, clagged-in day on Pen yr Helgi Du: summit wind broadly 15-30 mph, with gusts 25-35 mph during the evening (strong winds). A meaningful thunderstorm risk is indicated from the morning into the evening. Avoid committing to exposed ridges if storms begin to build. The ground is likely to be wet after recent rain. High spate risk based on forecast rainfall. Burns and unbridged crossings may become difficult or impassable. Most likely from around 00:00 until around 21:00. Cloud base mostly around 500–800 m through daylight. Expect clag for much of the day, though a brief clearance is possible during the evening. Cloud is likely to hang lowest on northwestern slopes; the southeastern side should see somewhat higher bases and better breaks. A persistently wet day is possible, with around 10-20 mm indicated; local totals could vary considerably. Confidence moderate (forecast models agree on the walking impact of the wind) - the summit peak could reasonably be 16-30 mph, so treat the headline as mid-range.

Forecast confidence: A low thunderstorm risk remains difficult to time precisely.

A rough, clagged-in day on Pen yr Helgi Du: summit wind broadly 10-25 mph, with gusts 20-30 mph during the morning (fresh and blowy). Thunderstorms are possible from around midday into the evening. Keep an escape route from exposed ridges and descend if thunder develops. The ground is likely to be saturated after recent rain. Expect boggy paths and rapid runoff if more rain arrives. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 08:00 until around 02:00 the following day. Cloud base around 400–700 m in the morning, then around 600–900 m around midday and 400–700 m by late afternoon. Expect the top to stay in cloud for most or all of daylight, with no dependable break. 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: Around 100% early, falling to around 0% later.

A wild day on Pen yr Helgi Du: 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 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 0–300 m in the morning, then around 900–1200 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. Some rain is likely, with up to around 2 mm indicated; timing and local totals remain uncertain. Confidence moderate (Summit wind could be roughly 26-46 mph, which changes how difficult exposed walking may feel) - the summit peak could reasonably be 26-46 mph, so treat the headline as mid-range.

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

Cloud-free timing: Around 0% early, improving to around 100% later.

A wild day on Pen yr Helgi Du: summit wind broadly 25-35 mph, with gusts 40-50 mph during the afternoon (gale-force winds). A meaningful thunderstorm risk is indicated from early morning into the evening. Avoid committing to exposed ridges if storms begin to build. The ground is likely to be wet after recent rain. There could be a spate risk based on forecast rainfall. Burns and unbridged crossings may rise quickly. Most likely from around 00:00 until around 23:00. Much calmer lower down - generally 10-20 mph in the valley, rising towards the tops. Cloud base around 400–700 m in the morning, lifting to 700–1000 m around midday and 1100–1400 m by late afternoon. 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 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 5-10 mm indicated; timing and local totals remain uncertain. Confidence moderate (Summit wind could be roughly 23-40 mph, which changes how difficult exposed walking may feel) - the summit peak could reasonably be 23-40 mph, so treat the headline as mid-range.