Mariehamn weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: June – August
What is the weather like in Mariehamn in September?
In September, Mariehamn is cool: daytime highs average 15 °C, and nights cool down to about 12 °C. The sea averages 14.0 °C – swimming is only for the hardy. Expect around 6 hours of sunshine a day. Rain falls on about 9 days, adding up to 44 mm. All in all, September is a good month for a holiday in Mariehamn.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 86 | 63 | 25 |
| Day | 18° | 15° | 10° |
| Night | 16° | 12° | 7° |
| Sea | 17° | 14° | 10° |
| Sun | 9 h | 6 h | 3 h |
| Rain days | 10 | 9 | 10 |
More details for September
- Daylight
- 13 h 0 min07:06 – 20:06
- UV index
- 2 · lowclear sky, noon (estimate)All months
- Muggy days
- 0 daysdew point 18 °C or moreAll months
- Wind
- 24 km/haverage daily peakAll months
- Cloud cover
- 61 %on averageAll months
- Hot days
- 0 days30 °C or more
- Snow days
- 0 days1 cm or more of fresh snowAll months
- Time zone
- UTC+3Europe/Mariehamn
How the score comes together
- Temperatureweight 50 %66 %
- Sunshineweight 20 %52 %
- Few rainy daysweight 30 %65 %
Each factor is rated from 0 to 100 % and weighted for the travel style “City break”.
What to pack in September
- A jumper for the evenings
- Rain jacket or umbrella
Mariehamn in September: quick answers
Is Mariehamn hot in September?
No. In September, Mariehamn is cool: daytime highs average 15 °C and nights drop to about 12 °C.
Can you swim in Mariehamn in September?
Only if you don't mind cold water: in September the sea averages just 14.0 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Mariehamn in September?
Rain falls on about 9 days, adding up to 44 mm.
Mariehamn month by month
The whole year in MariehamnAll destinations: Åland IslandsWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences