Climate averages 1991–2020
Mariehamn weather
in September.
A cool, moderately wet month: the 4th warmest and the 8th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a cool month in Mariehamn: daytime highs average 14.3°C and nights cool to about 11.8°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 54 mm of rain on roughly 9 days, which makes September a moderately wet month (the 8th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 57 min on an average September day.
The nearest other city in this atlas is Uppsala (130 km away). In September its highs average 15.6°C, 1.4°C warmer than Mariehamn, with 49 mm of rain.
From September to October, average highs fall by 5.2°C to 9.1°C, and monthly rainfall rises from 54 mm to 62 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
Mariehamn climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 1.0°C-1.6°C | -1.6°C | 43 | 10.5 | 6.87 h |
| February | -0.2°C-2.9°C | -2.9°C | 29 | 7.8 | 9.19 h |
| March | 1.5°C-1.5°C | -1.5°C | 27 | 7.1 | 11.712 h |
| April | 5.2°C1.8°C | 1.8°C | 29 | 6.9 | 14.515 h |
| May | 9.7°C6.1°C | 6.1°C | 33 | 6.6 | 17.117 h |
| June | 14.5°C10.9°C | 10.9°C | 49 | 7.5 | 18.719 h |
| July | 18.4°C15.1°C | 15.1°C | 48 | 7.6 | 18.018 h |
| August | 18.3°C15.4°C | 15.4°C | 55 | 10.2 | 15.716 h |
| September, selected | 14.3°C11.8°C | 11.8°C | 54 | 9.2 | 13.013 h |
| October | 9.1°C7.0°C | 7.0°C | 62 | 11.8 | 10.210 h |
| November | 5.3°C3.2°C | 3.2°C | 60 | 13.0 | 7.68 h |
| December | 2.8°C0.4°C | 0.4°C | 56 | 13.0 | 6.06 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
- Uppsala in SeptemberSweden · 130 kmHigh 15.6°C · Low 9.1°C · 49 mm rain
- Sollentuna in SeptemberSweden · 134 kmHigh 15.6°C · Low 9.9°C · 50 mm rain
- Turku in SeptemberFinland · 135 kmHigh 15.0°C · Low 8.8°C · 58 mm rain
- Stockholm in SeptemberSweden · 135 kmHigh 15.5°C · Low 10.5°C · 50 mm rain
- Haninge in SeptemberSweden · 144 kmHigh 15.1°C · Low 10.4°C · 51 mm rain
- Huddinge in SeptemberSweden · 146 kmHigh 15.5°C · Low 10.5°C · 50 mm rain
- Södertälje in SeptemberSweden · 164 kmHigh 15.9°C · Low 9.8°C · 51 mm rain
- Gävle in SeptemberSweden · 166 kmHigh 15.4°C · Low 9.2°C · 45 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 Mariehamn) is explained once on the Mariehamn year overview and on the Sources, method and limits page.