Siilinjärvi · April 2027
Northern lights in Siilinjärvi in April 2027
Answer
April against the rest of the year
April cloud at Siilinjärvi averages 71% in NASA POWER's 2001 to 2020 record, 4 points clearer than its yearly mean. June is Siilinjärvi's clearest month at 68%. By civil night times clear sky, April scores 2.1 hours at Siilinjärvi, 7th of 12. Kuopio, 21 km away, averages 73%, cloudier by 2 points.
Civil night at Siilinjärvi starts April at 8 h 45 min and reaches 5 h 8 min by April 30, 3.6 hours shorter. The 10 PM to 2 AM window is fully dark on 22 of 30 nights. The sun never reaches 18 degrees down, so Siilinjärvi gets no astronomical night in April.
April night by night
April opens toward a new moon on Apr 7, with full moon on Apr 21, in Europe/Helsinki dates. Siilinjärvi gets 117 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
8.8 h
- 2
17% lit
8.6 h
- 3
10% lit
8.5 h
- 4
5% lit
8.4 h
- 5
1% lit
8.3 h
- 6
0% lit
8.2 h
- 7
1% lit
7.5 h
- 8
4% lit
5.6 h
- 9
10% lit
3.5 h
- 10
18% lit
1.3 h
- 11
27% lit
0.0 h
- 12
38% lit
0.0 h
- 13
49% lit
0.0 h
- 14
61% lit
0.0 h
- 15
71% lit
0.0 h
- 16
81% lit
0.0 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
1.0 h
- 22
96% lit
2.9 h
- 23
91% lit
6.1 h
- 24
84% lit
6.0 h
- 25
77% lit
5.8 h
- 26
68% lit
5.7 h
- 27
59% lit
5.5 h
- 28
50% lit
5.4 h
- 29
40% lit
5.3 h
- 30
31% lit
5.1 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
Siilinjärvi needs Kp 3 for the average oval edge to sit overhead. 500 of the 900 April days from 1996 to 2025 (56%) reached it in the GFZ Potsdam record, one of the three most active months for that level; storm days with Kp 5 or more made up 12%. Siilinjärvi sits at 60.1 degrees geomagnetic, inside SWPC's 60 to 75 degree band, where aurora can be seen on more than half of all nights. No storm is needed: by SWPC's rule the average oval edge is overhead at Kp 3.
April across Finland
Siilinjärvi ranks 9th in Finland for civil night on April 15, behind Helsinki at 7.7 hours. Coming from March (10.6 hours at Siilinjärvi), April loses darkness, and May brings shorter nights (2.6 hours on the 15th).
Darkness and moon, every night
| Night | Civil | Astronomical | Moon-free dark | Moon-free, 10 PM to 2 AM | Moon lit |
|---|---|---|---|---|---|
| Thu Apr 1 | 8 h 45 min | 4 h | 8 h 45 min | 4 h | 25% |
| Fri Apr 2 | 8 h 38 min | 3 h 47 min | 8 h 38 min | 4 h | 17% |
| Sat Apr 3 | 8 h 31 min | 3 h 34 min | 8 h 31 min | 4 h | 10% |
| Sun Apr 4 | 8 h 24 min | 3 h 19 min | 8 h 24 min | 4 h | 5% |
| Mon Apr 5 | 8 h 17 min | 3 h 4 min | 8 h 17 min | 4 h | 1% |
| Tue Apr 6 | 8 h 10 min | 2 h 47 min | 8 h 10 min | 4 h | 0% |
| Wed Apr 7 | 8 h 3 min | 2 h 29 min | 7 h 29 min | 4 h | 1% |
| Thu Apr 8 | 7 h 56 min | 2 h 8 min | 5 h 34 min | 2 h 25 min | 4% |
| Fri Apr 9 | 7 h 49 min | 1 h 42 min | 3 h 29 min | 24 min | 10% |
| Sat Apr 10 | 7 h 42 min | 1 h 9 min | 1 h 16 min | 0 min | 18% |
| Sun Apr 11 | 7 h 35 min | 0 min | 0 min | 0 min | 27% |
| Mon Apr 12 | 7 h 28 min | 0 min | 0 min | 0 min | 38% |
| Tue Apr 13 | 7 h 21 min | 0 min | 0 min | 0 min | 49% |
| Wed Apr 14 | 7 h 13 min | 0 min | 0 min | 0 min | 61% |
| Thu Apr 15 | 7 h 6 min | 0 min | 0 min | 0 min | 71% |
| Fri Apr 16 | 6 h 58 min | 0 min | 0 min | 0 min | 81% |
| Sat Apr 17 | 6 h 51 min | 0 min | 0 min | 0 min | 89% |
| Sun Apr 18 | 6 h 44 min | 0 min | 0 min | 0 min | 95% |
| Mon Apr 19 | 6 h 36 min | 0 min | 0 min | 0 min | 99% |
| Tue Apr 20 | 6 h 28 min | 0 min | 0 min | 0 min | 100% |
| Wed Apr 21 | 6 h 21 min | 0 min | 1 h 1 min | 58 min | 99% |
| Thu Apr 22 | 6 h 13 min | 0 min | 2 h 55 min | 2 h 55 min | 96% |
| Fri Apr 23 | 6 h 5 min | 0 min | 6 h 5 min | 3 h 55 min | 91% |
| Sat Apr 24 | 5 h 57 min | 0 min | 5 h 57 min | 3 h 52 min | 84% |
| Sun Apr 25 | 5 h 49 min | 0 min | 5 h 49 min | 3 h 48 min | 77% |
| Mon Apr 26 | 5 h 41 min | 0 min | 5 h 41 min | 3 h 44 min | 68% |
| Tue Apr 27 | 5 h 33 min | 0 min | 5 h 33 min | 3 h 40 min | 59% |
| Wed Apr 28 | 5 h 25 min | 0 min | 5 h 25 min | 3 h 36 min | 50% |
| Thu Apr 29 | 5 h 16 min | 0 min | 5 h 16 min | 3 h 32 min | 40% |
| Fri Apr 30 | 5 h 8 min | 0 min | 5 h 8 min | 3 h 28 min | 31% |
Questions
- Can you see the northern lights in Siilinjärvi in April?
- On dark, clear nights with enough activity. 30 of 30 nights at Siilinjärvi have civil darkness, and 56% of past April days reached Kp 3.
- How dark is Siilinjärvi in April?
- Siilinjärvi averages 7.0 hours of civil night a night in April 2027, from 8 h 45 min on the 1st to 5 h 8 min on the last night.
- How cloudy is Siilinjärvi in April?
- NASA POWER's 2001 to 2020 climatology gives Siilinjärvi's 1 degree cell 71% mean cloud in April, against 75% for the whole year. It is an all-hours average, not a forecast.
- What is the best night in April 2027 for aurora in Siilinjärvi?
- By darkness and moon alone, Apr 1, with 4 h of moon-free darkness inside 10 PM to 2 AM at Siilinjärvi. Activity on that date will only be known hours ahead.
- Is April or May better in Siilinjärvi?
- By civil night times the clear share, April scores 2.1 hours at Siilinjärvi and May 0.8. 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.