Monthly Climate
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Best time to visit Mariehamn

July is the best time to visit Mariehamn for general sightseeing, with average highs of 19 °C and about 8 wet days. The comfortable season runs roughly July to August.

It depends what you are going for

One month rarely wins on everything. These are the best months on each measure taken on its own.

If you want Best month On that measure
Sightseeing and walking July comfort 83/100
A beach holiday August sea 17 °C
The least cloud May 52 % average cloud cover
The least rain March 28 mm
Warmth July 19 °C
Cooler weather February -0.2 °C

Ranked by comfort

# Month Comfort / 100 Avg high Wet days Beach
1 July 83 19 °C 8 35
2 August 80 18 °C 10 36
3 June 70 15 °C 8 16
4 September 67 14 °C 9 14
5 May 52 10 °C 7 17
6 October 43 9.1 °C 10 10
7 April 33 5.4 °C 7 16
8 November 28 5.3 °C 10 10
9 March 27 1.5 °C 7 18
10 February 25 -0.2 °C 7 17
11 December 23 2.8 °C 10 10
12 January 23 1.0 °C 9 14

For a beach holiday

August scores highest, with a sea temperature of 17 °C and air temperatures around 18 °C. The sea never reaches 20 °C here.

Month Sea Air Sunshine Beach score
January 2.4 °C 1.0 °C 78 % 14
February 1.3 °C -0.2 °C 75 % 17
March 1.3 °C 1.5 °C 65 % 18
April 2.5 °C 5.4 °C 59 % 16
May 5.6 °C 10 °C 52 % 17
June 11 °C 15 °C 54 % 16
July 16 °C 19 °C 52 % 35
August 17 °C 18 °C 57 % 36
September 14 °C 14 °C 60 % 14
October 9.7 °C 9.1 °C 70 % 10
November 6.7 °C 5.3 °C 78 % 10
December 4.2 °C 2.8 °C 77 % 10

When to think twice

January scores lowest with about 9 wet days and highs near 1.0 °C. That does not make it a bad month — it depends entirely on what you are travelling for. The numbers are all here; the judgement is yours.

The full year

Month Avg high Rainfall Cloud
January 1.0 °C 37 mm 78 %
February -0.2 °C 28 mm 75 %
March 1.5 °C 28 mm 65 %
April 5.4 °C 30 mm 59 %
May 10.1 °C 36 mm 52 %
June 14.7 °C 50 mm 54 %
July 18.6 °C 52 mm 52 %
August 18.4 °C 55 mm 57 %
September 14.3 °C 47 mm 60 %
October 9.1 °C 51 mm 70 %
November 5.3 °C 49 mm 78 %
December 2.8 °C 46 mm 77 %

Data sources and method

Normal period
1991–2020
Dataset version
era5-1991-2020-scores1.1
Last processed

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: comfort score, beach score, season boundaries. Full formulas are on the methodology page.

Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.