Can you see the northern lights in Mariehamn in December?

On dark, clear nights with enough activity. 31 of 31 nights at Mariehamn have civil darkness, and 19% of past December days reached Kp 4.

How dark is Mariehamn in December?

Mariehamn averages 15.9 hours of civil night a night in December 2026, from 15 h 37 min on the 1st to 15 h 57 min on the last night.

How cloudy is Mariehamn in December?

NASA POWER's 2001 to 2020 climatology gives Mariehamn's 1 degree cell 83% mean cloud in December, against 71% for the whole year. It is an all-hours average, not a forecast.

What is the best night in December 2026 for aurora in Mariehamn?

By darkness and moon alone, Dec 2, 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 December or January better in Mariehamn?

By civil night times the clear share, December scores 2.7 hours at Mariehamn and January 2.3. December comes out ahead.

Mariehamn · December 2026

Northern lights in Mariehamn in December 2026

Answer

December gives Mariehamn 16.0 hours of civil night on the 15th, the darkest month of its year, under 83% mean cloud. 19% of December days since 1996 reached Kp 4, enough for the oval edge to reach Mariehamn.

15.9 h

civil night, average night

SunCalc for 60.10, 19.93; NASA POWER; GFZ Kp

December 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

December cloud at Mariehamn averages 83% in NASA POWER's 2001 to 2020 record, 12 points cloudier than its yearly mean. June is Mariehamn's clearest month at 58%. By civil night times clear sky, December scores 2.7 hours at Mariehamn, 5th of 12. Uppsala, 130 km away, averages the same 83%.

Civil night at Mariehamn starts December at 15 h 37 min and reaches 15 h 57 min by December 31 as the nights lengthen by 0.3 hours. SWPC's 10 PM to 2 AM window is fully dark on every night. True astronomical darkness, the sun 18 degrees down, lasts 12.4 hours on the 15th.

December night by night

December opens toward a new moon on Dec 9, with full moon on Dec 24, in Europe/Mariehamn dates. Mariehamn gets 267 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: Dec 2 (4 h), Dec 3 (4 h), Dec 4 (4 h).

1
43% lit
8.3 h
2
33% lit
9.8 h
3
24% lit
11.3 h
4
16% lit
12.8 h
5
9% lit
14.4 h
6
4% lit
15.8 h
7
1% lit
15.8 h
8
0% lit
15.9 h
9
1% lit
15.9 h
New
10
3% lit
15.9 h
11
7% lit
15.7 h
12
13% lit
14.2 h
13
20% lit
12.7 h
14
28% lit
11.3 h
15
37% lit
9.8 h
16
47% lit
8.4 h
17
57% lit
7.0 h
18
67% lit
5.5 h
19
77% lit
3.8 h
20
86% lit
2.0 h
21
93% lit
0.2 h
22
98% lit
0.0 h
23
100% lit
0.0 h
24
99% lit
0.0 h
Full
25
95% lit
0.6 h
26
88% lit
2.5 h
27
80% lit
4.3 h
28
70% lit
5.9 h
29
59% lit
7.5 h
30
49% lit
9.0 h
31
39% lit
10.5 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 Decembers

Mariehamn needs Kp 4 for the average oval edge to sit overhead. 173 of the 930 December days from 1996 to 2025 (19%) reached it in the GFZ Potsdam record, one of the three quietest months for that level; storm days with Kp 5 or more made up 5%. 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.

December across Aland Islands

Coming from November (14.7 hours at Mariehamn), December adds darkness, and January brings shorter nights (15.4 hours on the 15th). The December solstice falls on December 21, 22:49 Mariehamn time.

Darkness and moon, every night

Mariehamn, December 2026: each night from local noon to the next noon
Night	Civil	Astronomical	Moon-free dark	Moon-free, 10 PM to 2 AM	Moon lit
Tue Dec 1	15 h 37 min	12 h 7 min	8 h 15 min	2 h 57 min	43%
Wed Dec 2	15 h 39 min	12 h 9 min	9 h 47 min	4 h	33%
Thu Dec 3	15 h 42 min	12 h 11 min	11 h 17 min	4 h	24%
Fri Dec 4	15 h 44 min	12 h 12 min	12 h 48 min	4 h	16%
Sat Dec 5	15 h 46 min	12 h 14 min	14 h 22 min	4 h	9%
Sun Dec 6	15 h 49 min	12 h 16 min	15 h 49 min	4 h	4%
Mon Dec 7	15 h 50 min	12 h 17 min	15 h 50 min	4 h	1%
Tue Dec 8	15 h 52 min	12 h 19 min	15 h 52 min	4 h	0%
Wed Dec 9	15 h 54 min	12 h 20 min	15 h 54 min	4 h	1%
Thu Dec 10	15 h 56 min	12 h 22 min	15 h 56 min	4 h	3%
Fri Dec 11	15 h 57 min	12 h 23 min	15 h 41 min	4 h	7%
Sat Dec 12	15 h 58 min	12 h 24 min	14 h 11 min	4 h	13%
Sun Dec 13	16 h	12 h 25 min	12 h 43 min	4 h	20%
Mon Dec 14	16 h 1 min	12 h 25 min	11 h 16 min	4 h	28%
Tue Dec 15	16 h 2 min	12 h 26 min	9 h 51 min	3 h 15 min	37%
Wed Dec 16	16 h 2 min	12 h 27 min	8 h 27 min	1 h 49 min	47%
Thu Dec 17	16 h 3 min	12 h 27 min	7 h	22 min	57%
Fri Dec 18	16 h 3 min	12 h 28 min	5 h 28 min	0 min	67%
Sat Dec 19	16 h 4 min	12 h 28 min	3 h 49 min	0 min	77%
Sun Dec 20	16 h 4 min	12 h 28 min	2 h 2 min	0 min	86%
Mon Dec 21	16 h 4 min	12 h 28 min	12 min	0 min	93%
Tue Dec 22	16 h 4 min	12 h 28 min	0 min	0 min	98%
Wed Dec 23	16 h 4 min	12 h 28 min	0 min	0 min	100%
Thu Dec 24	16 h 3 min	12 h 28 min	0 min	0 min	99%
Fri Dec 25	16 h 3 min	12 h 27 min	35 min	0 min	95%
Sat Dec 26	16 h 2 min	12 h 27 min	2 h 29 min	0 min	88%
Sun Dec 27	16 h 1 min	12 h 26 min	4 h 15 min	0 min	80%
Mon Dec 28	16 h	12 h 25 min	5 h 54 min	36 min	70%
Tue Dec 29	15 h 59 min	12 h 24 min	7 h 27 min	2 h 10 min	59%
Wed Dec 30	15 h 58 min	12 h 24 min	8 h 58 min	3 h 41 min	49%
Thu Dec 31	15 h 57 min	12 h 22 min	10 h 28 min	4 h	39%

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 December?: On dark, clear nights with enough activity. 31 of 31 nights at Mariehamn have civil darkness, and 19% of past December days reached Kp 4.
How dark is Mariehamn in December?: Mariehamn averages 15.9 hours of civil night a night in December 2026, from 15 h 37 min on the 1st to 15 h 57 min on the last night.
How cloudy is Mariehamn in December?: NASA POWER's 2001 to 2020 climatology gives Mariehamn's 1 degree cell 83% mean cloud in December, against 71% for the whole year. It is an all-hours average, not a forecast.
What is the best night in December 2026 for aurora in Mariehamn?: By darkness and moon alone, Dec 2, 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 December or January better in Mariehamn?: By civil night times the clear share, December scores 2.7 hours at Mariehamn and January 2.3. December 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.