Mariehamn climate

Name: Mariehamn
Address: AX

Mariehamn is warmest in July, with average highs of 19 °C, and coldest in February, when nights average -3.1 °C. August is the wettest month (55 mm) and March the driest (28 mm). Figures are 1991–2020 climate normals.

Across a full year Mariehamn averages 509 mm of rain, 1 days above 25 °C and 83 days below freezing.

Aland Islands · population 10,682 · 1991–2020 normals

Temperature below 0 °C to above 30 °C Rain band height is that month’s share of the wettest month

Warmest month July 19 °C
Coldest month February -3.1 °C
Driest month March 28 mm
Wettest month August 55 mm
Least cloud May 52 % cloud
Hottest on record July 30 °C
Coldest on record January -19 °C
Warmest sea August 17 °C

What to expectMariehamn through the year

Mariehamn has a clear annual cycle: average daily highs run from -0.2 °C in February to 19 °C in July, a swing of 18 °C in mean temperature across the year.

Counted across a normal year, 1 days a year reach 25 °C, 83 nights drop below freezing. The warmest reading in the 1991–2020 record is 30 °C, in July.

Rain is spread fairly evenly through the year, from 28 mm in March to 55 mm in August. There is no dry season to aim for.

The sea off Mariehamn is warmest in August at 17 °C and coldest in February at 1.3 °C. Sea temperature lags the air by a month or two, which is why late summer swims warmer than early summer at the same air temperature.

Month by month

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 %

Temperature month by month

Month	Avg high	Avg low	Mean	Record high	Record low	Days above 25 °C	Days below 0 °C
January	1.0 °C	-1.7 °C	-0.4 °C	9.5 °C	-18.8 °C	0	20
February	-0.2 °C	-3.1 °C	-1.6 °C	8.2 °C	-15.8 °C	0	21
March	1.5 °C	-1.7 °C	-0.0 °C	13.7 °C	-16.0 °C	0	19
April	5.4 °C	1.6 °C	3.6 °C	18.9 °C	-7.3 °C	0	6
May	10.1 °C	5.9 °C	8.1 °C	25.3 °C	-3.5 °C	0	0
June	14.7 °C	10.7 °C	12.9 °C	26.7 °C	3.3 °C	0	0
July	18.6 °C	14.8 °C	16.9 °C	30.0 °C	7.7 °C	1	0
August	18.4 °C	15.2 °C	16.9 °C	26.1 °C	8.6 °C	0	0
September	14.3 °C	11.5 °C	13.0 °C	21.4 °C	3.4 °C	0	0
October	9.1 °C	6.7 °C	8.0 °C	16.9 °C	-1.6 °C	0	0
November	5.3 °C	3.1 °C	4.2 °C	13.9 °C	-8.2 °C	0	4
December	2.8 °C	0.3 °C	1.6 °C	10.4 °C	-11.2 °C	0	13

Rain, sun and wind month by month

Month	Rainfall	Wet days	Daylight	Cloud cover	Humidity	Wind	Sea temp
January	37 mm	9	6.7 h/day	78 %	82 %	28 km/h	2.4 °C
February	28 mm	7	9.1 h/day	75 %	83 %	26 km/h	1.3 °C
March	28 mm	7	12 h/day	65 %	82 %	25 km/h	1.3 °C
April	30 mm	7	15 h/day	59 %	79 %	23 km/h	2.5 °C
May	36 mm	7	17 h/day	52 %	76 %	22 km/h	5.6 °C
June	50 mm	8	19 h/day	54 %	77 %	22 km/h	10.5 °C
July	52 mm	8	18 h/day	52 %	78 %	21 km/h	15.5 °C
August	55 mm	10	16 h/day	57 %	78 %	21 km/h	16.7 °C
September	47 mm	9	13 h/day	60 %	78 %	24 km/h	13.6 °C
October	51 mm	10	10 h/day	70 %	80 %	26 km/h	9.7 °C
November	49 mm	10	7.5 h/day	78 %	82 %	27 km/h	6.7 °C
December	46 mm	10	5.9 h/day	77 %	82 %	28 km/h	4.2 °C

How Mariehamn compares

The same four figures for nearby destinations, so the numbers above have something to be read against. Summer high is the warmest month's average high; winter low is the coldest month's average low.

Destination	Summer high	Winter low	Rain per year	Days above 25 °C
Mariehamn	19 °C	-3.1 °C	509 mm	1
Uppsala · Sweden	22 °C	-5.4 °C	569 mm	12
Stockholm · Sweden	21 °C	-4.0 °C	567 mm	7
Turku · Finland	22 °C	-7.3 °C	669 mm	10
Tampere · Finland	21 °C	-8.4 °C	630 mm	9

Where Mariehamn ranks

Ranking	Position	Value
The coolest places in Europe in May	8th of 50	10 °C
The coolest places in Europe in June	10th of 50	15 °C
The coolest places in Europe in April	14th of 50	5.4 °C
The coolest places in the world in May	14th of 50	10 °C
The coolest places in Europe in July	19th of 50	19 °C
The coolest places in the world in April	19th of 50	5.4 °C

Planning a trip? See the best time to visit Mariehamn.

QuestionsCommon questions about Mariehamn’s climate

When is the best time to visit Mariehamn?

That depends on what you want, so the honest answer is a comparison rather than a single month. July, August, September sit closest to 20 °C on average, July is the warmest month and March the driest. The month-by-month table above has the full picture.

How hot does Mariehamn get?

In July, the warmest month, daily highs average 19 °C. The highest value in the 1991–2020 record is 30 °C.

How cold does it get in winter?

Nights average -3.1 °C in February, the coldest month. A normal year has 83 nights below freezing.

Which month is wettest in Mariehamn?

August, averaging 55 mm over 10 days with rain. The driest month is March with 28 mm. The year as a whole averages 509 mm.

Are these figures a forecast?

No. They are 1991–2020 climate normals: the average of thirty years, which describes what a month is usually like in Mariehamn rather than what any particular week will bring. Individual years can differ substantially from the normal.

Data sources and method

ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
Open-Meteo — Open-Meteo.com. CC BY 4.0
NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
GeoNames — GeoNames.org. CC BY 4.0

Normal period: 1991–2020
Data point: 60.097°, 19.935° (the coordinates the reanalysis values are taken for)
Dataset version: era5-1991-2020-scores1.1
Last processed: 1 August 2026

Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: monthly rankings, daylight hours, beach and comfort scores. 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.