Click on a day for an hourly weather forecast
The temperatures in Trondheim in September are quite cold with temperatures between 7°C and 14°C, warm clothes are a must.
You can expect rain for roughly half of the month of September in Trondheim. We’re expecting roughly 8 to 15 days of rain, so your rubber boots and umbrella are going to see plenty of use this month if you’re keen on staying dry.
Our weather forecast can give you a great sense of what weather to expect in Trondheim in September 2025.
If you’re planning to visit Trondheim in the near future, we highly recommend that you review the 14 day weather forecast for Trondheim before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -3° / -7° | 6 | 11 | 14 | 92 mm | Awful | Trondheim in January |
| February | -2° / -6° | 6 | 7 | 15 | 92 mm | Awful | Trondheim in February |
| March | 2° / -4° | 9 | 6 | 17 | 131 mm | Awful | Trondheim in March |
| April | 6° / -1° | 8 | 12 | 10 | 88 mm | Awful | Trondheim in April |
| May | 12° / 4° | 8 | 18 | 5 | 84 mm | Awful | Trondheim in May |
| June | 16° / 8° | 9 | 21 | 0 | 118 mm | Ok | Trondheim in June |
| July | 19° / 10° | 8 | 23 | 0 | 108 mm | Ok | Trondheim in July |
| August | 18° / 9° | 8 | 23 | 0 | 132 mm | Ok | Trondheim in August |
| September | 14° / 7° | 8 | 22 | 0 | 121 mm | Ok | Trondheim in September |
| October | 8° / 3° | 9 | 20 | 2 | 110 mm | Awful | Trondheim in October |
| November | 2° / -1° | 7 | 17 | 6 | 80 mm | Awful | Trondheim in November |
| December | -2° / -5° | 10 | 8 | 13 | 96 mm | Awful | Trondheim in December |