A cloud inversion is one of the rarest, most photogenic conditions in UK hillwalking: valleys filled with white cloud while the summits stand clear in early morning sun. This tool pulls real forecast data from Open-Meteo and scores inversion likelihood across 20 UK mountain locations based on the conditions that actually matter: pressure, humidity, wind, temperature, and time of day.
Drag the time slider to explore the 72-hour forecast window. Click any marker for the full weather breakdown at that summit.
On still, clear nights, the valley floor loses heat faster than the air above it. Cold, dense air pools in the hollows, moisture condenses into cloud, and by dawn the lowlands are buried in white while the peaks stand free above them. From a summit, it looks like the hills are islands in a slow-moving sea.
Inversions are most common in autumn and winter (October to February), when nights are long enough for significant radiational cooling. They dissipate quickly once the sun warms the valley air, so the window is narrow: roughly 5am to 9am. Getting up early is not optional.
The predictor scores each location against eight conditions, weighted by how critical each one is:
Scores above 70% indicate most conditions are aligning; above 85% is exceptional. The cap at 85% is deliberate: weather is never a certainty.
The Lake District and Welsh mountains (particularly Pen y Fan, Cadair Idris, and the Glyders) produce the most consistently photographed inversions in England and Wales, thanks to their valley topography and accessible summits. The Brecon Beacons are the most practical option from the south of England: Pen y Fan is under two hours from Bristol, and the view from the north ridge above the Neuadd valley is as good as anything in Snowdonia.
Scottish mountains offer the most dramatic examples but require more of a commitment. Ben Nevis sits too high for the classic floating-island effect in most inversions; Ben Lawers and the Cairngorm plateau are better bets when conditions align in the Highlands.