Click on a day for an hourly weather forecast
The temperatures in Mariehamn in September are usually low and can range between 13°C and 14°C.
You can expect about 3 to 8 days of rain in Mariehamn during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Mariehamn in September 2025.
If you’re planning to visit Mariehamn in the near future, we highly recommend that you review the 14 day weather forecast for Mariehamn before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 1° / -1° | 4 | 13 | 15 | 49 mm | Awful | Mariehamn in January |
| February | 0° / -2° | 3 | 12 | 14 | 34 mm | Awful | Mariehamn in February |
| March | 1° / -1° | 5 | 16 | 11 | 33 mm | Awful | Mariehamn in March |
| April | 4° / 2° | 3 | 23 | 4 | 28 mm | Awful | Mariehamn in April |
| May | 8° / 6° | 4 | 26 | 1 | 44 mm | Ok | Mariehamn in May |
| June | 13° / 11° | 4 | 26 | 0 | 51 mm | Ok | Mariehamn in June |
| July | 17° / 15° | 4 | 27 | 0 | 63 mm | Good | Mariehamn in July |
| August | 18° / 16° | 5 | 26 | 0 | 86 mm | Good | Mariehamn in August |
| September | 14° / 13° | 4 | 26 | 0 | 69 mm | Good | Mariehamn in September |
| October | 9° / 8° | 7 | 24 | 0 | 70 mm | Bad | Mariehamn in October |
| November | 6° / 5° | 7 | 20 | 3 | 60 mm | Awful | Mariehamn in November |
| December | 3° / 1° | 6 | 14 | 10 | 60 mm | Awful | Mariehamn in December |