Tool
Rain probability by city and month
Pick a UK city and a month of travel and you'll see the chance of a wet day (>1mm), the average rainfall in mm, and how many days of the month are typically wet. Calibrated against the Met Office 1991–2020 averages for each city's main station.
Figures are 1991–2020 averages published by the Met Office for each city's primary observing station. They describe climate, not a particular week; in a wet year, monthly totals can run 1.4× the long-run mean.
What this solves
"It always rains in Manchester" is a stereotype with a kernel of truth, but the practical question is sharper: if I'm there in October, how many days should I expect to need a waterproof? The tool gives a single probability number per city/month so you can pack one waterproof jacket and a packable umbrella with confidence rather than second-guessing.
How to read the result
- Wet-day probability is the share of days in the month with at least 1mm of rain — the Met Office definition of a wet day.
- Monthly rainfall mm is the long-run total. Divide by rainy days to get the typical "wet day intensity".
- Rainy days count is the expected number of those wet days in a 30-day month for that average.
- What to pack is a short verdict you can act on directly.
What it doesn't cover
- The difference between drizzle and a proper downpour — the metric counts both.
- Coastal and upland stations: the Lake District, Snowdonia and the western Highlands run two to three times higher than these city figures.
- Thunderstorm days, which are short and unpredictable.
- Day-of-week or time-of-day distributions: rain in the UK can be remarkably front-loaded into weekday rush hours in some regions.
FAQ
When does the British rain season actually start?
The high-rain window is roughly October to January across most of the UK, peaking in November. Scotland's west coast stays wet all year; the south-east is the exception, with a real summer dip.
Is Manchester really the rainiest big city?
Not the rainiest in the UK overall — Glasgow and Cardiff both edge it for wet days — but it is the rainiest for rainfall volume among English cities. Manchester averages about 800mm a year, with October the wettest month at around 110–120mm.
Is there a proper dry summer?
In the south-east, yes — July often falls below 50mm with 7 or fewer wet days. In the north and west, summer is still wet: Manchester, Cardiff and Glasgow all run 70–110mm in July. The rest of the country sits in between.
What's the absolute wettest month on record?
For lowland cities, October or November. The Lake District and western Highlands run much higher — Seathwaite in Cumbria averages 250mm in October and well over 3000mm a year. Use this tool for lowland city averages; for those upland sites, expect figures roughly three times the on-screen number.
Sources
- UK Met Office — 1991–2020 climate averages for primary city stations.
- Met Office — UK regional rainfall series, monthly totals and wet-day counts.
- Met Office — Climate summaries for England NE/NW, Wales and Scotland.