Weather in Trondheim in May

A hard month. May is a hard month in Trondheim, and worth planning around. You should expect rain on 18 days of the month, which is more days wet than dry.

May ranks 5 of 12 in Trondheim: past the worst of the year but short of July, which is the month to book if the dates are open.

This is persistent light rain rather than storms: 18 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 12.8 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest May day reached 27.2 °C and the coldest night fell to -1.8 °C, and the wettest single day dropped 27 mm — roughly 29% of the month's rain in one day.

May is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest May on record still delivered 136 mm against 42 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 94 mm average is a reasonable planning figure, not a promise.

Wind is light at 3 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 80%, which at 12.8 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How May sits in the year

The month is on the way up: 4.9 °C warmer than April, and June adds another 3.7 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in May

18 hours of daylight, gaining 3 hours across the month. That is between Trondheim's extremes of 20.5 and 4.6 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 8.1 °C in May — 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

Shoulder. The value months — prices ease off and you get the place closer to itself.

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

May in Trondheim versus nearby

If Trondheim is one option among several, the nearby comparison is worth making. Oslo is a better bet in May — 2.7 °C warmer, 4 days less rain. Bergen is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: May works, with July the better month by 18 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Trondheim

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