Can you see the northern lights in Mariehamn in April?

On dark, clear nights with enough activity. 30 of 30 nights at Mariehamn have civil darkness, and 28% of past April days reached Kp 4.

How dark is Mariehamn in April?

Mariehamn averages 7.6 hours of civil night a night in April 2027, from 9 h 5 min on the 1st to 6 h 6 min on the last night.

How cloudy is Mariehamn in April?

NASA POWER's 2001 to 2020 climatology gives Mariehamn's 1 degree cell 61% mean cloud in April, against 71% for the whole year. It is an all-hours average, not a forecast.

What is the best night in April 2027 for aurora in Mariehamn?

By darkness and moon alone, Apr 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Mariehamn. Activity on that date will only be known hours ahead.

Is April or May better in Mariehamn?

By civil night times the clear share, April scores 3.0 hours at Mariehamn and May 1.8. April comes out ahead.

Mariehamn · April 2027

Northern lights in Mariehamn in April 2027

Answer

April gives Mariehamn 7.7 hours of civil night on the 15th, the 8th darkest of its 12 months, under 61% mean cloud. 28% of April days since 1996 reached Kp 4, enough for the oval edge to reach Mariehamn.

7.6 h

civil night, average night

SunCalc for 60.10, 19.93; NASA POWER; GFZ Kp

April against the rest of the year

2.3

2.4

3.1

3.0

1.8

0.3

1.2

2.4

3.3

2.8

2.4

2.7

April cloud at Mariehamn averages 61% in NASA POWER's 2001 to 2020 record, 10 points clearer than its yearly mean. June is Mariehamn's clearest month at 58%. By civil night times clear sky, April scores 3.0 hours at Mariehamn, 3rd of 12. Uppsala, 130 km away, averages 70%, cloudier by 9 points.

Civil night at Mariehamn starts April at 9 h 5 min and reaches 6 h 6 min by April 30, 3.0 hours shorter. The 10 PM to 2 AM window is fully dark on 19 of 30 nights. True astronomical darkness, the sun 18 degrees down, lasts 2.3 hours on the 15th.

April night by night

April opens toward a new moon on Apr 7, with full moon on Apr 21, in Europe/Mariehamn dates. Mariehamn gets 126 hours of civil night with the moon below the horizon across the month. The best of them for moon-free darkness inside 10 PM to 2 AM: Apr 1 (4 h), Apr 2 (4 h), Apr 3 (4 h).

1
25% lit
9.1 h
2
17% lit
9.0 h
3
10% lit
8.9 h
4
5% lit
8.8 h
5
1% lit
8.7 h
6
0% lit
8.6 h
7
1% lit
8.0 h
New
8
4% lit
6.2 h
9
10% lit
4.4 h
10
18% lit
2.8 h
11
27% lit
1.5 h
12
38% lit
0.8 h
13
49% lit
0.5 h
14
61% lit
0.3 h
15
71% lit
0.2 h
16
81% lit
0.1 h
17
89% lit
0.0 h
18
95% lit
0.0 h
19
99% lit
0.0 h
20
100% lit
0.0 h
21
99% lit
0.9 h
Full
22
96% lit
2.5 h
23
91% lit
4.0 h
24
84% lit
5.1 h
25
77% lit
5.7 h
26
68% lit
5.9 h
27
59% lit
6.0 h
28
50% lit
6.0 h
29
40% lit
6.0 h
30
31% lit
6.0 h

Each cell is the night that starts on that date. Hours are civil-dark time with the moon below the horizon; the green rule scales with them. Green outline: new moon. Bone outline: full moon.

Activity in past Aprils

Mariehamn needs Kp 4 for the average oval edge to sit overhead. 251 of the 900 April days from 1996 to 2025 (28%) reached it in the GFZ Potsdam record, 4th of 12 months; storm days with Kp 5 or more made up 12%. Mariehamn sits at 58.4 degrees geomagnetic. By SWPC's rule the average oval edge is overhead at Kp 4, and aurora is usually visible on the northern horizon at G1 (Kp 5) or less.

April across Aland Islands

Coming from March (10.7 hours at Mariehamn), April loses darkness, and May brings shorter nights (4.4 hours on the 15th).

Darkness and moon, every night

Mariehamn, April 2027: each night from local noon to the next noon
Night	Civil	Astronomical	Moon-free dark	Moon-free, 10 PM to 2 AM	Moon lit
Thu Apr 1	9 h 5 min	5 h 8 min	9 h 5 min	4 h	25%
Fri Apr 2	9 h	4 h 59 min	9 h	4 h	17%
Sat Apr 3	8 h 54 min	4 h 50 min	8 h 54 min	4 h	10%
Sun Apr 4	8 h 48 min	4 h 40 min	8 h 48 min	4 h	5%
Mon Apr 5	8 h 42 min	4 h 31 min	8 h 42 min	4 h	1%
Tue Apr 6	8 h 36 min	4 h 20 min	8 h 36 min	4 h	0%
Wed Apr 7	8 h 30 min	4 h 10 min	7 h 57 min	4 h	1%
Thu Apr 8	8 h 24 min	3 h 59 min	6 h 13 min	2 h 20 min	4%
Fri Apr 9	8 h 18 min	3 h 48 min	4 h 26 min	36 min	10%
Sat Apr 10	8 h 12 min	3 h 36 min	2 h 46 min	0 min	18%
Sun Apr 11	8 h 6 min	3 h 24 min	1 h 31 min	0 min	27%
Mon Apr 12	8 h	3 h 10 min	50 min	0 min	38%
Tue Apr 13	7 h 54 min	2 h 56 min	30 min	0 min	49%
Wed Apr 14	7 h 47 min	2 h 41 min	18 min	0 min	61%
Thu Apr 15	7 h 41 min	2 h 25 min	11 min	0 min	71%
Fri Apr 16	7 h 35 min	2 h 6 min	6 min	0 min	81%
Sat Apr 17	7 h 29 min	1 h 44 min	1 min	0 min	89%
Sun Apr 18	7 h 23 min	1 h 17 min	0 min	0 min	95%
Mon Apr 19	7 h 16 min	32 min	0 min	0 min	99%
Tue Apr 20	7 h 10 min	0 min	0 min	0 min	100%
Wed Apr 21	7 h 4 min	0 min	54 min	54 min	99%
Thu Apr 22	6 h 57 min	0 min	2 h 30 min	2 h 30 min	96%
Fri Apr 23	6 h 51 min	0 min	3 h 58 min	3 h 47 min	91%
Sat Apr 24	6 h 45 min	0 min	5 h 5 min	3 h 44 min	84%
Sun Apr 25	6 h 38 min	0 min	5 h 41 min	3 h 41 min	77%
Mon Apr 26	6 h 32 min	0 min	5 h 56 min	3 h 38 min	68%
Tue Apr 27	6 h 25 min	0 min	6 h	3 h 35 min	59%
Wed Apr 28	6 h 19 min	0 min	6 h 1 min	3 h 32 min	50%
Thu Apr 29	6 h 12 min	0 min	6 h	3 h 29 min	40%
Fri Apr 30	6 h 6 min	0 min	5 h 58 min	3 h 26 min	31%

Moon lit: SunCalc illuminated fraction at the middle of the 10 PM to 2 AM window.

Questions

Can you see the northern lights in Mariehamn in April?: On dark, clear nights with enough activity. 30 of 30 nights at Mariehamn have civil darkness, and 28% of past April days reached Kp 4.
How dark is Mariehamn in April?: Mariehamn averages 7.6 hours of civil night a night in April 2027, from 9 h 5 min on the 1st to 6 h 6 min on the last night.
How cloudy is Mariehamn in April?: NASA POWER's 2001 to 2020 climatology gives Mariehamn's 1 degree cell 61% mean cloud in April, against 71% for the whole year. It is an all-hours average, not a forecast.
What is the best night in April 2027 for aurora in Mariehamn?: By darkness and moon alone, Apr 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Mariehamn. Activity on that date will only be known hours ahead.
Is April or May better in Mariehamn?: By civil night times the clear share, April scores 3.0 hours at Mariehamn and May 1.8. April comes out ahead.

Sources and verification

SunCalchttps://github.com/mourner/suncalc
NASA POWER climatologyhttps://power.larc.nasa.gov/docs/services/api/temporal/climatology/
GFZ Potsdam Kp indexhttps://kp.gfz.de/en/data
NOAA SWPC, Tips on viewing the aurorahttps://www.spaceweather.gov/content/tips-viewing-aurora

Quoted figures last checked against their sources on 2026-09-30; next review 2026-12-31. Computed figures come from SunCalc and the IGRF-14 dipole as described in the methodology. Every quote is listed in the sources ledger.