Trondheim weather in September
September in Trondheim: cool, rainy, with clean air — a great time to visit.
Updated September 2026 · climate normals from ERA5 reanalysis
#5 of 12 months in Trondheim · #869 of 1413 destinations to visit in September · comfort 75/100 (tier B)
- Days
- 16°C
- Nights
- 8°C
- Wet days
- 12
- Sun
- 7.2 h
- Humidity
- 83%
- Daylight
- 13 h

Traveller notes on Trondheim in September
Notes from nearby Åre (134 km away)
Trondheim doesn't have its own notes for September yet — these are about Åre, close enough to share the season.
Forum posters describe September in Sweden generally as a good time to visit once the summer crowds thin out, though weather is genuinely unpredictable - conditions can range from a warm, sunny 25C spell to a cold, rainy 12C stretch within the same month, with early September typically a safer bet than the back half, which tends to turn rainier. Posters recommend a flexible layering system: t-shirts for a mild day, a medium-weight sweater or cardigan for cooler stretches, and a lightweight water-resistant coat for when the rain arrives. As a mountain town well north of Stockholm, Are itself should be expected to run cooler and see more rain days than the milder southern-Sweden figures posters typically quote, given both the latitude and elevation.
Other months in Trondheim
Forum posters describe December in Trondheim as bringing short, cold days with ground typically covered in snow, noting that locals lean toward cross-country skiing rather than walking this time of year. Posters are direct that heavy snow arriving right before or during a visit can rule out most walking plans entirely, though the tram ride up to Lian is consistently flagged as a safe, reliable option regardless of conditions. Posters consistently recommend wool long underwear along with a hat and gloves as genuine essentials, noting that special outerwear pants aren't really needed for strolling around the city itself. Posters flag that many students leave for the holidays, leaving Trondheim noticeably quieter than usual through late December. Posters generally rate December as workable but genuinely weather-dependent, with flexibility the key to enjoying a winter visit.
June in Trondheim barely gets dark — over twenty hours of daylight — and the forum's own saying is that if you are not happy with the weather, give it five minutes. Expect 10 to 20°C, some nights down to 5, occasional days above 25, and the honest possibility of cold, windy and rainy instead. They call June relatively dry, though the record still shows rain on about thirteen days. The packing list is a list precisely because you may need all of it: windproof and waterproof shell, a woollen sweater, long trousers, hiking shoes, and shorts. June versus July is not worth agonising over — the difference is statistical.
Add your own note from Trondheim's card on the map.
Trondheim climate normals — September
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Trondheim in September
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
BusyAutumn break in Norway, school holidays in 3 of the markets that fill it(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Trondheim's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Fair weatherTrondheim's weather peaks June–August, best around July.
Best weatherFair weatherToughest weather
What's on in Trondheim in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Season
Pilgrim walking season
1 Jun – 15 Sep · usuallyTrail seasonThe St Olav Ways into Nidaros are walkable once the snow is off the Dovre passes, and the hostels along them open for the season. Walkers arrive at the cathedral all summer, thickest in the week before Olsok. Source ↗
- Nature
Aurora season
15 Sep – 31 Mar · usuallyFar enough south that it takes an active night rather than any dark one, but on those nights the lights are visible from the Bymarka hills fifteen minutes out of the centre. Coastal cloud is the usual spoiler.
Nearby, and something's on
Within 300 km of Trondheim — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Trondheim?
Trondheim in September — FAQ
- Is September a good time to visit Trondheim?
- September in Trondheim: cool, rainy, with clean air — a great time to visit. It ranks #5 of 12 months for Trondheim on SeasonMap's comfort score (75/100).
- What is the weather like in Trondheim in September?
- In September, Trondheim averages a daily high of 15.8°C and a low of 8.4°C, with about 96.2 mm of rain over roughly 12.2 rainy days.
- What is the air quality in Trondheim in September?
- Trondheim has a mean US Air Quality Index of about 27 in September.
Within 300 km: Åre's Are autumn market around 20–30 Sep, and Geiranger's Dalsnibba and Eagle Road open around 20 May – 5 Nov.