Climate averages 1991–2020
Trondheim weather
in September.
A cool, wet month: the 4th warmest and the wettest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a cool month in Trondheim: daytime highs average 14.0°C and nights cool to about 7.3°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 102 mm of rain on roughly 15 days, which makes September a wet month (the wettest month of the year). Daylight, from sunrise to sunset, lasts about 13 h 06 min on an average September day.
The nearest other city in this atlas is Lillestrøm (388 km away). In September its highs average 15.0°C, 1.0°C warmer than Trondheim, with 81 mm of rain.
Among the 8 cities listed in Norway, Trondheim ranks 8th of 8 for the warmest September highs and 5th of 8 for the driest September (rainfall, lowest first). The mean September high of those 8 cities is 15.0°C; Trondheim is 1.0°C cooler than that mean.
From September to October, average highs fall by 6.2°C to 7.8°C, and monthly rainfall falls from 102 mm to 87 mm.
The annual picture
September in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Trondheim climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -1.1°C-6.1°C | -6.1°C | 96 | 16.0 | 5.86 h |
| February | -0.5°C-6.1°C | -6.1°C | 86 | 14.5 | 8.69 h |
| March | 2.9°C-3.8°C | -3.8°C | 88 | 15.4 | 11.712 h |
| April | 7.8°C-0.4°C | -0.4°C | 67 | 13.6 | 14.915 h |
| May | 12.5°C3.8°C | 3.8°C | 70 | 15.6 | 18.118 h |
| June | 15.9°C8.1°C | 8.1°C | 95 | 15.6 | 20.320 h |
| July | 18.6°C10.8°C | 10.8°C | 85 | 14.8 | 19.319 h |
| August | 17.9°C10.6°C | 10.6°C | 99 | 14.9 | 16.316 h |
| September, selected | 14.0°C7.3°C | 7.3°C | 102 | 14.8 | 13.113 h |
| October | 7.8°C2.2°C | 2.2°C | 87 | 15.2 | 9.910 h |
| November | 2.3°C-2.4°C | -2.4°C | 79 | 13.2 | 6.87 h |
| December | -0.6°C-5.7°C | -5.7°C | 94 | 15.3 | 4.85 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Lillestrøm in SeptemberNorway · 388 kmHigh 15.0°C · Low 8.6°C · 81 mm rain
- Oslo in SeptemberNorway · 392 kmHigh 15.5°C · Low 9.5°C · 89 mm rain
- Drammen in SeptemberNorway · 410 kmHigh 15.8°C · Low 9.7°C · 94 mm rain
- Bergen in SeptemberNorway · 429 kmHigh 14.2°C · Low 9.1°C · 249 mm rain
- Gävle in SeptemberSweden · 466 kmHigh 15.4°C · Low 9.2°C · 45 mm rain
- Fredrikstad in SeptemberNorway · 469 kmHigh 15.6°C · Low 10.6°C · 81 mm rain
- Umeå in SeptemberSweden · 489 kmHigh 13.0°C · Low 8.3°C · 62 mm rain
- Örebro in SeptemberSweden · 528 kmHigh 15.6°C · Low 9.4°C · 55 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Trondheim) is explained once on the Trondheim year overview and on the Sources, method and limits page.