Climate Insights for Mariehamn

The climate in Mariehamn is cool. The average annual temperature is 8°C and approximately 552mm of precipitation falls per year. October is the wettest month, receiving around 67mm of rainfall. Mariehamn is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: August, July, September. The coldest months are February, January, March, when temperatures can drop to -1°C. Snowfall occurs from January to December, with around 65cm accumulating over the season.

Mariehamn sees moderate temperature variation throughout the year, ranging from -1°C to 18°C. August is the warmest month, though highs remain moderate at 18°C with a mean of 17°C. The coldest month is February, when overnight lows fall to -1°C and the daily average is 1°C. Daily temperature variation is modest, with an average difference of 2°C between highs and lows. The sharpest temperature change occurs between May and June, with a 6°C shift in average temperatures.

Mariehamn is a relatively dry area, receiving approximately 552mm of precipitation annually, which averages out to around 46mm per month. The wettest month is October, averaging 67mm of rainfall. November and August also tend to see above-average precipitation. The driest month is April, with just 25mm. That's 42mm less than October, the wettest month. Precipitation varies noticeably between seasons, with the second half (July to December) of the year generally seeing more rainfall. Snowfall is a regular feature from January to December, with around 65cm accumulating over the season. January typically sees the most snow at around 19cm.

Mariehamn is very windy, with an average annual wind speed of 32km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is January, averaging 39km/h, which can feel quite blustery and may affect outdoor activities. The calmest conditions occur in July, with average winds dropping to 27km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 12km/h gap between the calmest and windiest months. Wind tends to be stronger during winter months, driven by seasonal pressure systems. The seasonal averages break down to 37km/h in winter, 30km/h in spring, 28km/h in summer, 33km/h in autumn.

It is currently spring in Mariehamn, which began on March 20, 2026. Mariehamn is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in August at around 18°C, while the coldest stretch bottoms out in February near -1°C. Summer is next, beginning on June 21, 2026 — 89 days from now.

The best time to visit Mariehamn is during July and August, when the weather is most comfortable for travellers. During these months, average temperatures hover around 17°C with modest rainfall averaging 53mm per month. By contrast, February can be quite cold with temperatures dropping to -1°C. A light rain jacket is recommended, though showers are generally brief and shouldn't disrupt your plans.

The table below shows monthly climate averages for Mariehamn based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.