Mariehamn · May 2027
Northern lights in Mariehamn in May 2027
Answer
May against the rest of the year
May cloud at Mariehamn averages 59% in NASA POWER's 2001 to 2020 record, 12 points clearer than its yearly mean. June is Mariehamn's clearest month at 58%. By civil night times clear sky, May scores 1.8 hours at Mariehamn, 10th of 12. Uppsala, 130 km away, averages 69%, cloudier by 10 points.
Civil night at Mariehamn starts May at 5 h 59 min and reaches 2 h 31 min by May 31, 3.5 hours shorter. No night keeps the 10 PM to 2 AM window fully dark at Mariehamn. The sun never reaches 18 degrees down, so Mariehamn gets no astronomical night in May.
May night by night
May opens toward a new moon on May 6, with full moon on May 20, in Europe/Mariehamn dates. Mariehamn gets 71 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: May 1 (3 h 23 min), May 2 (3 h 20 min), May 3 (3 h 16 min).
- 1
22% lit
5.9 h
- 2
15% lit
5.9 h
- 3
8% lit
5.8 h
- 4
3% lit
5.7 h
- 5
1% lit
5.5 h
- 6
0% lit
5.4 h
- 7
3% lit
3.7 h
- 8
8% lit
2.2 h
- 9
15% lit
1.3 h
- 10
25% lit
0.9 h
- 11
35% lit
0.7 h
- 12
46% lit
0.5 h
- 13
58% lit
0.4 h
- 14
69% lit
0.3 h
- 15
78% lit
0.2 h
- 16
86% lit
0.2 h
- 17
93% lit
0.1 h
- 18
97% lit
0.0 h
- 19
99% lit
0.0 h
- 20
100% lit
0.1 h
- 21
98% lit
1.4 h
- 22
94% lit
2.1 h
- 23
89% lit
2.5 h
- 24
82% lit
2.6 h
- 25
75% lit
2.6 h
- 26
66% lit
2.6 h
- 27
57% lit
2.6 h
- 28
47% lit
2.5 h
- 29
38% lit
2.5 h
- 30
28% lit
2.4 h
- 31
19% lit
2.4 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 Mays
Mariehamn needs Kp 4 for the average oval edge to sit overhead. 206 of the 930 May days from 1996 to 2025 (22%) reached it in the GFZ Potsdam record, 8th of 12 months; storm days with Kp 5 or more made up 10%. 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.
May across Aland Islands
Coming from April (7.7 hours at Mariehamn), May loses darkness, and June brings shorter nights (0.6 hours on the 15th).
Darkness and moon, every night
| Night | Civil | Astronomical | Moon-free dark | Moon-free, 10 PM to 2 AM | Moon lit |
|---|---|---|---|---|---|
| Sat May 1 | 5 h 59 min | 0 min | 5 h 55 min | 3 h 23 min | 22% |
| Sun May 2 | 5 h 53 min | 0 min | 5 h 53 min | 3 h 20 min | 15% |
| Mon May 3 | 5 h 46 min | 0 min | 5 h 46 min | 3 h 16 min | 8% |
| Tue May 4 | 5 h 39 min | 0 min | 5 h 39 min | 3 h 13 min | 3% |
| Wed May 5 | 5 h 33 min | 0 min | 5 h 33 min | 3 h 10 min | 1% |
| Thu May 6 | 5 h 26 min | 0 min | 5 h 26 min | 3 h 7 min | 0% |
| Fri May 7 | 5 h 19 min | 0 min | 3 h 40 min | 1 h 24 min | 3% |
| Sat May 8 | 5 h 13 min | 0 min | 2 h 13 min | 0 min | 8% |
| Sun May 9 | 5 h 6 min | 0 min | 1 h 20 min | 0 min | 15% |
| Mon May 10 | 4 h 59 min | 0 min | 53 min | 0 min | 25% |
| Tue May 11 | 4 h 52 min | 0 min | 39 min | 0 min | 35% |
| Wed May 12 | 4 h 45 min | 0 min | 30 min | 0 min | 46% |
| Thu May 13 | 4 h 39 min | 0 min | 24 min | 0 min | 58% |
| Fri May 14 | 4 h 32 min | 0 min | 19 min | 0 min | 69% |
| Sat May 15 | 4 h 25 min | 0 min | 14 min | 0 min | 78% |
| Sun May 16 | 4 h 18 min | 0 min | 10 min | 0 min | 86% |
| Mon May 17 | 4 h 11 min | 0 min | 4 min | 0 min | 93% |
| Tue May 18 | 4 h 4 min | 0 min | 0 min | 0 min | 97% |
| Wed May 19 | 3 h 57 min | 0 min | 0 min | 0 min | 99% |
| Thu May 20 | 3 h 50 min | 0 min | 5 min | 5 min | 100% |
| Fri May 21 | 3 h 43 min | 0 min | 1 h 21 min | 1 h 21 min | 98% |
| Sat May 22 | 3 h 36 min | 0 min | 2 h 7 min | 2 h 7 min | 94% |
| Sun May 23 | 3 h 28 min | 0 min | 2 h 28 min | 2 h 7 min | 89% |
| Mon May 24 | 3 h 21 min | 0 min | 2 h 36 min | 2 h 4 min | 82% |
| Tue May 25 | 3 h 14 min | 0 min | 2 h 37 min | 2 h | 75% |
| Wed May 26 | 3 h 7 min | 0 min | 2 h 36 min | 1 h 56 min | 66% |
| Thu May 27 | 3 h | 0 min | 2 h 34 min | 1 h 53 min | 57% |
| Fri May 28 | 2 h 53 min | 0 min | 2 h 31 min | 1 h 49 min | 47% |
| Sat May 29 | 2 h 45 min | 0 min | 2 h 28 min | 1 h 45 min | 38% |
| Sun May 30 | 2 h 38 min | 0 min | 2 h 26 min | 1 h 41 min | 28% |
| Mon May 31 | 2 h 31 min | 0 min | 2 h 24 min | 1 h 38 min | 19% |
Questions
- Can you see the northern lights in Mariehamn in May?
- On dark, clear nights with enough activity. 31 of 31 nights at Mariehamn have civil darkness, and 22% of past May days reached Kp 4.
- How dark is Mariehamn in May?
- Mariehamn averages 4.3 hours of civil night a night in May 2027, from 5 h 59 min on the 1st to 2 h 31 min on the last night.
- How cloudy is Mariehamn in May?
- NASA POWER's 2001 to 2020 climatology gives Mariehamn's 1 degree cell 59% mean cloud in May, against 71% for the whole year. It is an all-hours average, not a forecast.
- What is the best night in May 2027 for aurora in Mariehamn?
- By darkness and moon alone, May 1, with 3 h 23 min of moon-free darkness inside 10 PM to 2 AM at Mariehamn. Activity on that date will only be known hours ahead.
- Is May or June better in Mariehamn?
- By civil night times the clear share, May scores 1.8 hours at Mariehamn and June 0.3. May 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.