Mariehamn weather in September

In September, Mariehamn sees average daytime highs of 14°C and overnight lows near 13°C, with 54 mm of rain across 9.2 wet days and about 12.6 hours of daylight. It is the 3rd-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 16°C in the first days to 12°C by the end. The sky is clear or mostly clear about 27% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 54 min at the start of September to 11 h 12 min by month's end. Set against the rest of the year, September is Mariehamn's 6th-clearest and 7th-windiest month. For the whole year in context, see Mariehamn's year-round climate.

Daytime high: 14°; 3rd warmest
Overnight low: 13°; 10th coldest
Rainfall: 54 mm; 9.2 wet days
Daylight: 12 h 30 min; 6:18 AM – 6:51 PM
Cloud cover: 60%; 6th clearest
Wind: 24 km/h; 7th windiest
Solar energy: 2.8 kWh/m²
Travel score: 4.1; out of 10

← August Mariehamn year-round climate October →Best places to visit in September

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 16°C in the first days to 12°C by the end.

A typical September day in Mariehamn reaches about 14°C in the afternoon and slips back to 13°C overnight — a 2°C spread between the day's warmth and the night's chill. On most days the high lands between 12°C and 16°C. Set against its neighbours, September runs about 4°C cooler than August and about 5°C warmer than October.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Avg high (°C)	16	16	16	16	16	15	15	15	15	15	15	15	14	14	14	14	14	14	14	13	13	13	13	13	13	13	12	12	12	12
Avg low (°C)	15	14	14	14	14	14	14	14	13	13	13	13	13	13	13	12	12	12	12	12	12	12	11	11	11	11	11	11	11	10

	Avg high (°C)	Avg low (°C)
1	16	15
2	16	14
3	16	14
4	16	14
5	16	14
6	15	14
7	15	14
8	15	14
9	15	13
10	15	13
11	15	13
12	15	13
13	14	13
14	14	13
15	14	13
16	14	12
17	14	12
18	14	12
19	14	12
20	13	12
21	13	12
22	13	12
23	13	11
24	13	11
25	13	11
26	13	11
27	12	11
28	12	11
29	12	11
30	12	10

How September really feels in Mariehamn

Once humidity and wind are folded in, September averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C

heat index over the day's high

Days feeling ≤ 0°C

wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Mariehamn weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 5th-wettest month here — the current month is highlighted below.

Month	High / Low (°C)	Rainfall (mm)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	2° / -1°	43	10.5	8	6.4	0.0
Feb	0° / -2°	29	7.7	6.5	8.6	0.0
Mar	1° / -1°	27	7.1	5.1	11.3	0.0
Apr	4° / 2°	29	6.9	1.7	14.2	0.0
May	8° / 6°	33	6.6	0.2	16.8	1.6
Jun	13° / 11°	49	7.5	0	18.4	3.8
Jul	17° / 15°	48	7.6	0	17.7	5.9
Aug	18° / 16°	55	10.2	0	15.4	5.8
Sep	14° / 13°	54	9.2	0	12.6	4.1
Oct	9° / 8°	62	11.8	0.4	9.8	1.9
Nov	6° / 4°	60	13	2.9	7.1	0.4
Dec	3° / 1°	56	13	6.1	5.6	0.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 27% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 20% of September, with mostly cloudy or overcast conditions the remaining 53%.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Clearer (%)	47	47	47	47	48	49	49	50	50	49	49	50	50	49	48	48	48	48	47	47	46	46	46	46	46	45	44	44	44	43
Cloudier (%)	53	53	53	53	52	51	51	50	50	51	51	50	50	51	52	52	52	52	53	53	54	54	54	54	54	55	56	56	56	57

	Clearer (%)	Cloudier (%)
1	47	53
2	47	53
3	47	53
4	47	53
5	48	52
6	49	51
7	49	51
8	50	50
9	50	50
10	49	51
11	49	51
12	50	50
13	50	50
14	49	51
15	48	52
16	48	52
17	48	52
18	48	52
19	47	53
20	47	53
21	46	54
22	46	54
23	46	54
24	46	54
25	46	54
26	45	55
27	44	56
28	44	56
29	44	56
30	43	57

Chance of precipitation in September

Any precipitation

Mariehamn gets around 54 mm of rain over 9.2 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 32% and peaks near 36% on the wettest days.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Rain chance (%)	36	36	35	35	34	34	34	34	33	33	33	33	33	32	32	31	31	30	30	30	29	29	29	29	29	29	29	29	30	31

	Rain chance (%)
1	36
2	36
3	35
4	35
5	34
6	34
7	34
8	34
9	33
10	33
11	33
12	33
13	33
14	32
15	32
16	31
17	31
18	30
19	30
20	30
21	29
22	29
23	29
24	29
25	29
26	29
27	29
28	29
29	30
30	31

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the dry band about 82% of days. It rarely turns muggy — the humid and sticky bands barely register.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Dry (%)	58	59	61	62	64	67	68	71	73	75	78	80	81	83	85	88	89	90	91	93	93	94	95	95	96	96	97	97	97	98
Comfortable (%)	34	34	33	33	32	30	29	27	25	23	21	19	18	16	14	12	11	10	9	7	7	6	5	5	4	4	3	3	3	2
Humid (%)	8	7	6	5	4	3	3	2	2	2	1	1	1	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

	Dry (%)	Comfortable (%)	Humid (%)
1	58	34	8
2	59	34	7
3	61	33	6
4	62	33	5
5	64	32	4
6	67	30	3
7	68	29	3
8	71	27	2
9	73	25	2
10	75	23	2
11	78	21	1
12	80	19	1
13	81	18	1
14	83	16	1
15	85	14	1
16	88	12	0
17	89	11	0
18	90	10	0
19	91	9	0
20	93	7	0
21	93	7	0
22	94	6	0
23	95	5	0
24	95	5	0
25	96	4	0
26	96	4	0
27	97	3	0
28	97	3	0
29	97	3	0
30	98	2	0

Wind in September

Winds average 24 km/h in September.

Across September, daily wind ranges from about 24 km/h on the calmest days to 25 km/h at its breeziest. It stays fairly steady from day to day.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Wind speed (km/h)	24	24	24	24	24	24	24	24	24	24	24	24	24	24	24	24	24	24	25	25	25	25	25	25	25	25	25	25	25	25
Feels	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy	breezy

	Wind speed (km/h)	Feels
1	24	breezy
2	24	breezy
3	24	breezy
4	24	breezy
5	24	breezy
6	24	breezy
7	24	breezy
8	24	breezy
9	24	breezy
10	24	breezy
11	24	breezy
12	24	breezy
13	24	breezy
14	24	breezy
15	24	breezy
16	24	breezy
17	24	breezy
18	24	breezy
19	25	breezy
20	25	breezy
21	25	breezy
22	25	breezy
23	25	breezy
24	25	breezy
25	25	breezy
26	25	breezy
27	25	breezy
28	25	breezy
29	25	breezy
30	25	breezy

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 54 min at the start of September to 11 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 162 minutes over September. Sunrise moves from 5:42 AM to 6:53 AM, and sunset from 7:38 PM to 6:06 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Daylight (h)	13.9	13.8	13.7	13.7	13.6	13.5	13.4	13.3	13.2	13.1	13.0	12.9	12.8	12.7	12.6	12.5	12.4	12.4	12.3	12.2	12.1	12.0	11.9	11.8	11.7	11.6	11.5	11.4	11.3	11.2
Sunrise (AM)	5:42	5:44	5:47	5:49	5:52	5:54	5:57	5:59	6:01	6:04	6:06	6:09	6:11	6:14	6:16	6:18	6:21	6:23	6:26	6:28	6:31	6:33	6:36	6:38	6:40	6:43	6:45	6:48	6:50	6:53
Sunset (PM)	7:38	7:35	7:32	7:29	7:26	7:22	7:19	7:16	7:13	7:10	7:07	7:03	7:00	6:57	6:54	6:51	6:48	6:44	6:41	6:38	6:35	6:32	6:28	6:25	6:22	6:19	6:16	6:13	6:10	6:06

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	13.9	5:42	7:38
2	13.8	5:44	7:35
3	13.7	5:47	7:32
4	13.7	5:49	7:29
5	13.6	5:52	7:26
6	13.5	5:54	7:22
7	13.4	5:57	7:19
8	13.3	5:59	7:16
9	13.2	6:01	7:13
10	13.1	6:04	7:10
11	13.0	6:06	7:07
12	12.9	6:09	7:03
13	12.8	6:11	7:00
14	12.7	6:14	6:57
15	12.6	6:16	6:54
16	12.5	6:18	6:51
17	12.4	6:21	6:48
18	12.4	6:23	6:44
19	12.3	6:26	6:41
20	12.2	6:28	6:38
21	12.1	6:31	6:35
22	12.0	6:33	6:32
23	11.9	6:36	6:28
24	11.8	6:38	6:25
25	11.7	6:40	6:22
26	11.6	6:43	6:19
27	11.5	6:45	6:16
28	11.4	6:48	6:13
29	11.3	6:50	6:10
30	11.2	6:53	6:06

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.8 kWh/m².

For context, solar energy here swings from a low near 0.18 kWh/m² to a high of 6.29 kWh/m² in June across the year — September's 2.8 kWh/m² falls in the middle.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Solar energy (kWh/m²)	3.6	3.5	3.5	3.4	3.4	3.3	3.2	3.2	3.1	3.1	3.0	3.0	2.9	2.9	2.8	2.8	2.7	2.7	2.6	2.6	2.5	2.5	2.4	2.4	2.3	2.2	2.2	2.1	2.1	2.0
Level	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate

	Solar energy (kWh/m²)	Level
1	3.6	Moderate
2	3.5	Moderate
3	3.5	Moderate
4	3.4	Moderate
5	3.4	Moderate
6	3.3	Moderate
7	3.2	Moderate
8	3.2	Moderate
9	3.1	Moderate
10	3.1	Moderate
11	3.0	Moderate
12	3.0	Moderate
13	2.9	Moderate
14	2.9	Moderate
15	2.8	Moderate
16	2.8	Moderate
17	2.7	Moderate
18	2.7	Moderate
19	2.6	Moderate
20	2.6	Moderate
21	2.5	Moderate
22	2.5	Moderate
23	2.4	Moderate
24	2.4	Moderate
25	2.3	Moderate
26	2.2	Moderate
27	2.2	Moderate
28	2.1	Moderate
29	2.1	Moderate
30	2.0	Moderate

Planning a trip in September

Is September a good time to visit Mariehamn?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

4.1

Sightseeing

3rd-best month of the year

0.1

Beach & pool

3rd-best month of the year

September is a reasonable time to visit Mariehamn for sightseeing.

What to pack for Mariehamn in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Mariehamn sees daytime highs around 14°C and nights near 13°C. Worth packing: a warm layer, rain gear and a windbreaker. About 9 days see rain.

a warm layerrain geara windbreaker

Sea temperature near Mariehamn in September

The nearest coast averages about 14°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in August at about 17°C and coldest in February near 1°C.

The water stays below 20°C all year — cool enough that most swimmers want a wetsuit.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Sea temperature (°C)	2	1	1	3	6	11	16	17	14	10	7	4
Comfort	Bracing	Bracing	Bracing	Bracing	Bracing	Bracing	Cool	Cool	Bracing	Bracing	Bracing	Bracing

	Sea temperature (°C)	Comfort
Jan	2	Bracing
Feb	1	Bracing
Mar	1	Bracing
Apr	3	Bracing
May	6	Bracing
Jun	11	Bracing
Jul	16	Cool
Aug	17	Cool
Sep	14	Bracing
Oct	10	Bracing
Nov	7	Bracing
Dec	4	Bracing

UV index in Mariehamn in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 3. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Mariehamn peaks around June 18 at about 5 (high) — a little sun protection helps at midday. It bottoms out near December 20 at about 0 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 4 months of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	0	1	1	3	4	5	5	4	3	1	0	0
Level	Low	Low	Low	Moderate	Moderate	High	Moderate	Moderate	Moderate	Low	Low	Low

	UV index (midday)	Level
Jan	0	Low
Feb	1	Low
Mar	1	Low
Apr	3	Moderate
May	4	Moderate
Jun	5	High
Jul	5	Moderate
Aug	4	Moderate
Sep	3	Moderate
Oct	1	Low
Nov	0	Low
Dec	0	Low

Location & terrain

Where is Mariehamn?

Mariehamn sits at 60.1°N, 19.9°E, 11 m above sea level, in Aland Islands. The nearest listed city is Norrtälje, 78 km away.

Topography around Mariehamn

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Mariehamn.

Within 3 km, the terrain around Mariehamn has only modest variations in elevation — a maximum elevation change of 55 m around an average of 7 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 80 m; within 80 km, only modest variations in elevation — a maximum elevation change of 130 m.

The land around Mariehamn is covered by water (44%) and trees (32%) within 3 km, water (55%) and trees (31%) within 16 km, and water (86%) within 80 km.

3 km

55 m

water 44%

16 km

80 m

water 55%

80 km

130 m

water 86%

treesgrasslandcroplandartificial surfaceswaterwetland

← August Mariehamn year-round climate October →Best places to visit in September

September weather nearby: Norrtälje 78 km · Åkersberga 114 km · Vallentuna 121 km · Gustavsberg 122 km · Naantali 122 km · Boo 126 km · Täby 127 km · Märsta 128 km

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Mariehamn (60.0973°, 19.9348°, elevation 11 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).

	Avg high (°C)	Avg low (°C)
1	16	15
2	16	14
3	16	14
4	16	14
5	16	14
6	15	14
7	15	14
8	15	14
9	15	13
10	15	13
11	15	13
12	15	13
13	14	13
14	14	13
15	14	13
16	14	12
17	14	12
18	14	12
19	14	12
20	13	12
21	13	12
22	13	12
23	13	11
24	13	11
25	13	11
26	13	11
27	12	11
28	12	11
29	12	11
30	12	10

	Clearer (%)	Cloudier (%)
1	47	53
2	47	53
3	47	53
4	47	53
5	48	52
6	49	51
7	49	51
8	50	50
9	50	50
10	49	51
11	49	51
12	50	50
13	50	50
14	49	51
15	48	52
16	48	52
17	48	52
18	48	52
19	47	53
20	47	53
21	46	54
22	46	54
23	46	54
24	46	54
25	46	54
26	45	55
27	44	56
28	44	56
29	44	56
30	43	57

	Rain chance (%)
1	36
2	36
3	35
4	35
5	34
6	34
7	34
8	34
9	33
10	33
11	33
12	33
13	33
14	32
15	32
16	31
17	31
18	30
19	30
20	30
21	29
22	29
23	29
24	29
25	29
26	29
27	29
28	29
29	30
30	31

	Dry (%)	Comfortable (%)	Humid (%)
1	58	34	8
2	59	34	7
3	61	33	6
4	62	33	5
5	64	32	4
6	67	30	3
7	68	29	3
8	71	27	2
9	73	25	2
10	75	23	2
11	78	21	1
12	80	19	1
13	81	18	1
14	83	16	1
15	85	14	1
16	88	12	0
17	89	11	0
18	90	10	0
19	91	9	0
20	93	7	0
21	93	7	0
22	94	6	0
23	95	5	0
24	95	5	0
25	96	4	0
26	96	4	0
27	97	3	0
28	97	3	0
29	97	3	0
30	98	2	0

	Avg high (°C)	Avg low (°C)
1	16	15
2	16	14
3	16	14
4	16	14
5	16	14
6	15	14
7	15	14
8	15	14
9	15	13
10	15	13
11	15	13
12	15	13
13	14	13
14	14	13
15	14	13
16	14	12
17	14	12
18	14	12
19	14	12
20	13	12
21	13	12
22	13	12
23	13	11
24	13	11
25	13	11
26	13	11
27	12	11
28	12	11
29	12	11
30	12	10

	Clearer (%)	Cloudier (%)
1	47	53
2	47	53
3	47	53
4	47	53
5	48	52
6	49	51
7	49	51
8	50	50
9	50	50
10	49	51
11	49	51
12	50	50
13	50	50
14	49	51
15	48	52
16	48	52
17	48	52
18	48	52
19	47	53
20	47	53
21	46	54
22	46	54
23	46	54
24	46	54
25	46	54
26	45	55
27	44	56
28	44	56
29	44	56
30	43	57

	Rain chance (%)
1	36
2	36
3	35
4	35
5	34
6	34
7	34
8	34
9	33
10	33
11	33
12	33
13	33
14	32
15	32
16	31
17	31
18	30
19	30
20	30
21	29
22	29
23	29
24	29
25	29
26	29
27	29
28	29
29	30
30	31

	Dry (%)	Comfortable (%)	Humid (%)
1	58	34	8
2	59	34	7
3	61	33	6
4	62	33	5
5	64	32	4
6	67	30	3
7	68	29	3
8	71	27	2
9	73	25	2
10	75	23	2
11	78	21	1
12	80	19	1
13	81	18	1
14	83	16	1
15	85	14	1
16	88	12	0
17	89	11	0
18	90	10	0
19	91	9	0
20	93	7	0
21	93	7	0
22	94	6	0
23	95	5	0
24	95	5	0
25	96	4	0
26	96	4	0
27	97	3	0
28	97	3	0
29	97	3	0
30	98	2	0

	Avg high (°C)	Avg low (°C)
1	16	15
2	16	14
3	16	14
4	16	14
5	16	14
6	15	14
7	15	14
8	15	14
9	15	13
10	15	13
11	15	13
12	15	13
13	14	13
14	14	13
15	14	13
16	14	12
17	14	12
18	14	12
19	14	12
20	13	12
21	13	12
22	13	12
23	13	11
24	13	11
25	13	11
26	13	11
27	12	11
28	12	11
29	12	11
30	12	10

	Clearer (%)	Cloudier (%)
1	47	53
2	47	53
3	47	53
4	47	53
5	48	52
6	49	51
7	49	51
8	50	50
9	50	50
10	49	51
11	49	51
12	50	50
13	50	50
14	49	51
15	48	52
16	48	52
17	48	52
18	48	52
19	47	53
20	47	53
21	46	54
22	46	54
23	46	54
24	46	54
25	46	54
26	45	55
27	44	56
28	44	56
29	44	56
30	43	57

	Rain chance (%)
1	36
2	36
3	35
4	35
5	34
6	34
7	34
8	34
9	33
10	33
11	33
12	33
13	33
14	32
15	32
16	31
17	31
18	30
19	30
20	30
21	29
22	29
23	29
24	29
25	29
26	29
27	29
28	29
29	30
30	31

	Dry (%)	Comfortable (%)	Humid (%)
1	58	34	8
2	59	34	7
3	61	33	6
4	62	33	5
5	64	32	4
6	67	30	3
7	68	29	3
8	71	27	2
9	73	25	2
10	75	23	2
11	78	21	1
12	80	19	1
13	81	18	1
14	83	16	1
15	85	14	1
16	88	12	0
17	89	11	0
18	90	10	0
19	91	9	0
20	93	7	0
21	93	7	0
22	94	6	0
23	95	5	0
24	95	5	0
25	96	4	0
26	96	4	0
27	97	3	0
28	97	3	0
29	97	3	0
30	98	2	0