Weather in Köln in December

The month to avoid. Of the twelve, December is the one to avoid. Highs sit at 5.5 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

December ranks 11 of 12 — near the bottom of Köln's year. September is the month that works, and the swing between the two is 56 points, which is a different holiday rather than a slightly better one.

This is persistent light rain rather than storms: 15 wet days but only 2 heavy ones. It rarely cancels anything outright, and it rarely fully clears either. A jacket beats an umbrella. Layers, and a genuinely waterproof outer — at 5.5 °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: 14 nights fall below freezing; the day barely swings — 5.1 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 14.8 °C and the coldest night fell to -12.6 °C.

December is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest December on record still delivered 130 mm against 24 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 77 mm average is a reasonable planning figure, not a promise.

Wind is light at 12.1 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 93%, which at 5.5 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How December sits in the year

Temperatures hold steady either side: 9.8 °C in November, 5.5 here, 4.8 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Köln's year — 8 hours of daylight against 16.5 at midsummer, losing 0.4 hours across the 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 — 25.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

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

December in Köln versus nearby

If Köln is one option among several, the nearby comparison is worth making. Frankfurt am Main is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Bielefeld is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: December is a compromise. September is 54 points better and is what Köln 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 Köln

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