Joensuu · May 2027
Northern lights in Joensuu in May 2027
Answer
May against the rest of the year
May cloud at Joensuu averages 74% in NASA POWER's 2001 to 2020 record, 2 points clearer than its yearly mean. August is Joensuu's clearest month at 70%. By civil night times clear sky, May scores 0.8 hours at Joensuu, 10th of 12. Kuopio, 111 km away, averages 72%, clearer by 2 points.
Civil night at Joensuu starts May at 5 h 10 min and reaches 0 min by May 31, 5.2 hours shorter. 7 Joensuu nights this month have no civil darkness at all. No night keeps the 10 PM to 2 AM window fully dark at Joensuu. The sun never reaches 18 degrees down, so Joensuu 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/Helsinki dates. Joensuu gets 37 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 38 min), May 2 (3 h 34 min), May 3 (3 h 29 min).
- 1
22% lit
5.2 h
- 2
15% lit
5.0 h
- 3
8% lit
4.9 h
- 4
3% lit
4.8 h
- 5
1% lit
4.6 h
- 6
0% lit
4.5 h
- 7
3% lit
2.4 h
- 8
8% lit
0.7 h
- 9
15% lit
0.0 h
- 10
25% lit
0.0 h
- 11
35% lit
0.0 h
- 12
46% lit
0.0 h
- 13
58% lit
0.0 h
- 14
69% lit
0.0 h
- 15
78% lit
0.0 h
- 16
86% lit
0.0 h
- 17
93% lit
0.0 h
- 18
97% lit
0.0 h
- 19
99% lit
0.0 h
- 20
100% lit
0.0 h
- 21
98% lit
1.7 h
- 22
94% lit
1.4 h
- 23
89% lit
1.1 h
- 24
82% lit
0.5 h
- 25
75% lit
no night
- 26
66% lit
no night
- 27
57% lit
no night
- 28
47% lit
no night
- 29
38% lit
no night
- 30
28% lit
no night
- 31
19% lit
no night
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
Joensuu 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%. Joensuu sits at 59.4 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 Finland
Joensuu ranks 8th in Finland for civil night on May 15, behind Helsinki at 4.4 hours. Coming from April (7.2 hours at Joensuu), May loses darkness, and June brings shorter nights (0.0 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 10 min | 0 min | 5 h 10 min | 3 h 38 min | 22% |
| Sun May 2 | 5 h 2 min | 0 min | 5 h 2 min | 3 h 34 min | 15% |
| Mon May 3 | 4 h 54 min | 0 min | 4 h 54 min | 3 h 29 min | 8% |
| Tue May 4 | 4 h 45 min | 0 min | 4 h 45 min | 3 h 25 min | 3% |
| Wed May 5 | 4 h 37 min | 0 min | 4 h 37 min | 3 h 21 min | 1% |
| Thu May 6 | 4 h 28 min | 0 min | 4 h 28 min | 3 h 17 min | 0% |
| Fri May 7 | 4 h 19 min | 0 min | 2 h 26 min | 1 h 20 min | 3% |
| Sat May 8 | 4 h 10 min | 0 min | 40 min | 0 min | 8% |
| Sun May 9 | 4 h 1 min | 0 min | 0 min | 0 min | 15% |
| Mon May 10 | 3 h 52 min | 0 min | 0 min | 0 min | 25% |
| Tue May 11 | 3 h 42 min | 0 min | 0 min | 0 min | 35% |
| Wed May 12 | 3 h 32 min | 0 min | 0 min | 0 min | 46% |
| Thu May 13 | 3 h 22 min | 0 min | 0 min | 0 min | 58% |
| Fri May 14 | 3 h 12 min | 0 min | 0 min | 0 min | 69% |
| Sat May 15 | 3 h 1 min | 0 min | 0 min | 0 min | 78% |
| Sun May 16 | 2 h 50 min | 0 min | 0 min | 0 min | 86% |
| Mon May 17 | 2 h 38 min | 0 min | 0 min | 0 min | 93% |
| Tue May 18 | 2 h 26 min | 0 min | 0 min | 0 min | 97% |
| Wed May 19 | 2 h 13 min | 0 min | 0 min | 0 min | 99% |
| Thu May 20 | 1 h 59 min | 0 min | 0 min | 0 min | 100% |
| Fri May 21 | 1 h 44 min | 0 min | 1 h 44 min | 1 h 44 min | 98% |
| Sat May 22 | 1 h 26 min | 0 min | 1 h 26 min | 1 h 26 min | 94% |
| Sun May 23 | 1 h 4 min | 0 min | 1 h 4 min | 1 h 4 min | 89% |
| Mon May 24 | 31 min | 0 min | 31 min | 31 min | 82% |
| Tue May 25 | 0 min | 0 min | 0 min | 0 min | 75% |
| Wed May 26 | 0 min | 0 min | 0 min | 0 min | 66% |
| Thu May 27 | 0 min | 0 min | 0 min | 0 min | 57% |
| Fri May 28 | 0 min | 0 min | 0 min | 0 min | 47% |
| Sat May 29 | 0 min | 0 min | 0 min | 0 min | 38% |
| Sun May 30 | 0 min | 0 min | 0 min | 0 min | 28% |
| Mon May 31 | 0 min | 0 min | 0 min | 0 min | 19% |
Questions
- Can you see the northern lights in Joensuu in May?
- On dark, clear nights with enough activity. 24 of 31 nights at Joensuu have civil darkness, and 22% of past May days reached Kp 4.
- How dark is Joensuu in May?
- Joensuu averages 2.5 hours of civil night a night in May 2027, from 5 h 10 min on the 1st to 0 min on the last night.
- How cloudy is Joensuu in May?
- NASA POWER's 2001 to 2020 climatology gives Joensuu's 1 degree cell 74% mean cloud in May, against 76% for the whole year. It is an all-hours average, not a forecast.
- What is the best night in May 2027 for aurora in Joensuu?
- By darkness and moon alone, May 1, with 3 h 38 min of moon-free darkness inside 10 PM to 2 AM at Joensuu. Activity on that date will only be known hours ahead.
- Is May or June better in Joensuu?
- By civil night times the clear share, May scores 0.8 hours at Joensuu and June 0.0. 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.