Weather in Seoul in December

The month to avoid. Of the twelve, December is the one to avoid. Highs sit at 2.9 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 12 of 12 — near the bottom of Seoul's year. May is the month that works, and the swing between the two is 53 points, which is a different holiday rather than a slightly better one.

Rain falls on only 5 days, so an itinerary with no wet-weather fallback is a reasonable risk. Layers, and a genuinely waterproof outer — at 2.9 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: 25 nights drop below freezing, so anything left outside stays frozen. Across the twenty years measured, the hottest December day reached 14.5 °C and the coldest night fell to -16.3 °C, and the wettest single day dropped 26 mm — roughly 118% of the month's rain in one day.

December is moderately variable: 3 mm in the driest year against 50 mm in the wettest, around an average of 22 mm. Roughly two Decembers in three land near that average, and the third does something else entirely.

Wind is light at 12 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 76%, which at 2.9 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

The month is on the way down: 8 °C cooler than November, with January dropping another 2.1 °C. The first week and the last are not the same trip.

Daylight in December

December sits at the dark end of Seoul's year — 9.6 hours of daylight against 14.7 at midsummer, holding steady all month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

An inland climate

With no coast nearby, the year swings a fair way — 35.2 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

December in Seoul versus nearby

If Seoul is one option among several, the nearby comparison is worth making. Daegu is close enough to be a coin toss — 2.5 °C warmer, 1 day less rain. Gwangju is a better bet in December — 3.7 °C warmer, 2 days more rain.

So: December is a compromise. May is 53 points better and is what Seoul is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Seoul

See all twelve months in Seoul, or where else to go in December.