From the WeatherDuck archive
The UK Cloud Inversion Report 2026
When are cloud inversions most likely in the UK? We scored more than 13,000 archived mornings, reaching back to 2021, with the same forecast formula and the same Possible, Likely and Very likely bands WeatherDuck runs today. Here is the short, honest version of what it shows.
The short version
Four things the archive shows
1. The season is real
Mornings reaching our Likely band cluster heavily in late autumn and winter: 6.9% of October mornings, 3.9% in December and 2.8% in November in our main archive, against 0.4% or less for every month from April to September. The smaller archive reaching back to 2021, scored the same way, repeats the shape with December and January on top and summer empty. June is the emptiest month of all: across 885 scored June mornings, not one reached Likely.
2. No two years are the same
The season always arrives, but no single month can be trusted with it. October 2025 reached Likely on nearly one morning in eight, six times more often than October 2024. November swung the opposite way: strong in 2024, completely blank in 2025. The older archive tells the same story: December 2021 reached Likely on roughly one morning in twelve, then the two Decembers after it were blank. Somewhere between October and January the good mornings will come; which month carries them changes every year, so treat the whole window as the season and be ready to move when a settled spell locks in.
3. Most mornings, nowhere works
Only 1 morning in 67 reached the Likely band, and 1 in 113 reached Very likely. On 611 of the 662 days we scored, not a single monitored location got there anywhere in the UK. Inversions are rare events, which is why catching one feels the way it does.
4. The best mornings are national
When a big inversion sets up, it tends to set up almost everywhere at once. On 11 and 12 October 2025, 9 of the 15 locations we monitor reached Likely or better on the same dawns, from Dartmoor to the north west Highlands. Big inversions ride on country sized areas of high pressure.
The season, drawn
Likely mornings by month
Share of scored mornings reaching each band, by month. Roughly 900 scored mornings sit behind each month.
Likely Very likely
Percentage of scored mornings reaching Likely, with the Very likely share inside it. Individual months vary a lot from year to year; the overall shape is the reliable part.
Method, in one paragraph
Where these numbers come from
WeatherDuck reconstructs the lower atmosphere above a consistent set of monitored UK locations using UK Met Office high resolution model data supplied through Open-Meteo. The main archive behind this report covers 15 locations over 662 consecutive days, August 2024 to June 2026, and every rate on this page comes from that set: 9,930 mornings. A smaller archive of three locations reaches back to January 2021 and was scored with the same formula; its older weather data reads slightly conservative, so we use it to confirm the pattern rather than for exact rates. Together that is 13,647 mornings, all judged by one identical bar, the same Possible, Likely and Very likely ladder the site runs today. Reaching a band here means the local signal reached that strength; the live map only shows a Likely area when several nearby points agree, so this page speaks about signal strength, not map areas. These are model reconstructions rather than observations, two years shows the seasonal shape but cannot promise what any single month will deliver, and we will rerun and update this page as the archive grows. The full method is documented in how WeatherDuck forecasts cloud inversions, and we publish hits and misses alike in the verification hub.
Use the findings
Planning your own inversion morning
Check the live UK cloud inversion forecast and predictor for the next 24 hours, free and without an account. A free account adds an email alert for the mountain you watch, so the next settled spell does not slip past you.
For writers and researchers
Citing this report
Journalists, bloggers and outdoor writers are welcome to reuse the findings and numbers on this page with a credit and a link. For questions about the data or additional breakdowns, contact WeatherDuck through the contact page.