UK Weather by Month: London Gets Half Seoul's Annual Rain — It's the Frequency and the Short Days

London's average annual rainfall is 719 mm, barely half of Seoul's 1,300 mm. Britain's rainy reputation comes from frequency, not volume: London sees rain on 9–13 days almost every month. Seoul gets half its year's rain in the July–August monsoon; London gets a little, often, all year round.

The other number that shapes a British trip is day length: Edinburgh gets 17.6 hours in June and 7.0 in December. A city that's dark before 4 p.m. and one that's light until 10 p.m. call for completely different plans. Temperatures are gentler than Seoul's: London's January nights (1.6°C) are 8°C milder, and its July afternoons (22.9°C) 6°C cooler.

London rain tends to come and go rather than set in. A bright morning, a lunchtime shower and a sunny afternoon is an ordinary day, which is why locals reach for a hooded waterproof more often than an umbrella — and why umbrellas so often turn inside out in the wind.

Edinburgh's July high is 18.6°C — Seoul in late April. But in June the sun is up for over 17 hours, so you can watch it set over the castle at 10 p.m. August brings the Edinburgh festivals (the Fringe and others) and the year's highest hotel prices. In winter the sun sets before 4 p.m., and the Hogmanay new-year celebrations on 31 December are the one winter peak.

North-west England, home to Manchester and Liverpool, catches Atlantic rain first: 1,180 mm a year, 1.6 times London's. If you're going for football, most of the August–May season is wet winter, so a waterproof jacket and shoes are essential.

Clothing advice is for London; go one step warmer in Edinburgh all year. Day length is sunrise to sunset on the 15th of each month.

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The right British packing list isn't one thick layer but three thin ones; the weather changes several times a day.

• Period and source: daily values from Open-Meteo's historical weather data (ERA5 reanalysis), 2016–2025, averaged by month at each city-centre coordinate.
• Versus official normals: reanalysis temperatures usually land within 1–2°C of station normals, but downpours get smoothed out, so monthly rain totals come out lower and rainy-day counts slightly higher. Day length is not observed; it is sunrise-to-sunset on the 15th of each month, computed from latitude.
• Rainy day: at least 1 mm of precipitation. Reanalysis picks up even light showers, so counts run high — especially in the tropics, where monthly millimetres are the better guide. Most tropical rain is an hour or two of downpour, not a washed-out day.
• Best months: a first pass from temperature, rainy days and humidity, then adjusted for seasonal factors such as the Edinburgh festivals, Christmas and Hogmanay, and short winter days. It is a judgement call.