South Korea weather by month

In Seoul, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.

The clearer part of the year begins around September 24 and lasts for 6.8 months, ending around April 17. The clearest month is October, when the sky is clear, mostly clear, or partly cloudy 66% of the time on average.

The cloudier part of the year begins around April 18 and lasts for 5.2 months, ending around September 23. The cloudiest month is July, when it is overcast or mostly cloudy 67% of the time.

This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.

Wind in Seoul is steady company: average speeds sit near 9 km/h — calm — in every month of the year, with no meaningful windy or calm season.

Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.

Seoul receives about 4.1 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 2.3 and 6.0 kWh/m².

The brighter stretch of the year lasts 6.8 months, from around Mar 2 to Sep 24. The brightest month is May, averaging about 5.8 kWh/m² (bright).

The dimmest month is December, down near 2.4 kWh/m² — roughly 59% less than the May peak.