Weather in Trondheim in December

The month to avoid. December is the month most people should skip in Trondheim. Highs sit at 1 °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 Trondheim's year. July is the month that works, and the swing between the two is 54 points, which is a different holiday rather than a slightly better one.

Rain on 20 of the month's 31 days, 5 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Layers, and a genuinely waterproof outer — at 1 °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: 21 nights drop below freezing, so anything left outside stays frozen; the day barely swings — 4 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest December day reached 8.9 °C and the coldest night fell to -18.9 °C, and the wettest single day dropped 31 mm — roughly 22% of the month's rain in one day.

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 267 mm against 37 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 140 mm average is a reasonable planning figure, not a promise.

Wind is light at 5.3 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 96%, which at 1 °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: 3.1 °C in November, 1 here, -0.2 in January. Nothing about the timing within the month matters much.

Daylight in December

December sits at the dark end of Trondheim's year — 4.6 hours of daylight against 20.5 at midsummer, losing 0.8 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 7.8 °C in December — too cold to swim without a wetsuit. The sea peaks at 14.2 °C in August and bottoms out at 6.1 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

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 Trondheim versus nearby

If Trondheim is one option among several, the nearby comparison is worth making. Oslo is close enough to be a coin toss — 2.3 °C cooler, 6 days less rain. Bergen is close enough to be a coin toss — within a degree on temperature, 3 days more rain.

So: December is a compromise. July is 52 points better and is what Trondheim 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 Trondheim

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