Forssa · August 2027
Northern lights in Forssa in August 2027
Answer
August against the rest of the year
August cloud at Forssa averages 63% in NASA POWER's 2001 to 2020 record, 9 points clearer than its yearly mean. May is Forssa's clearest month at 62%. By civil night times clear sky, August scores 2.3 hours at Forssa, 8th of 12. Tampere, 77 km away, averages 65%, cloudier by 2 points.
Civil night at Forssa starts August at 4 h 38 min and reaches 8 h by August 31 as the nights lengthen by 3.4 hours. The 10 PM to 2 AM window is fully dark on 11 of 31 nights. The sun never reaches 18 degrees down, so Forssa gets no astronomical night in August.
August night by night
August opens toward a new moon on Aug 2 and Aug 31, with full moon on Aug 17, in Europe/Helsinki dates. Forssa gets 98 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: Aug 29 (4 h), Aug 30 (4 h), Aug 31 (4 h).
- 1
0% lit
4.6 h
- 2
0% lit
4.8 h
- 3
3% lit
4.9 h
- 4
9% lit
5.0 h
- 5
17% lit
5.1 h
- 6
26% lit
5.2 h
- 7
36% lit
5.3 h
- 8
47% lit
5.5 h
- 9
57% lit
5.6 h
- 10
67% lit
5.7 h
- 11
76% lit
5.8 h
- 12
83% lit
4.8 h
- 13
90% lit
3.5 h
- 14
95% lit
2.0 h
- 15
98% lit
0.5 h
- 16
100% lit
0.0 h
- 17
100% lit
0.0 h
- 18
98% lit
0.0 h
- 19
94% lit
0.0 h
- 20
88% lit
0.0 h
- 21
81% lit
0.0 h
- 22
73% lit
0.0 h
- 23
63% lit
0.0 h
- 24
53% lit
0.0 h
- 25
42% lit
0.0 h
- 26
31% lit
0.8 h
- 27
21% lit
2.3 h
- 28
12% lit
4.3 h
- 29
5% lit
6.2 h
- 30
1% lit
7.9 h
- 31
0% lit
8.0 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 Augusts
Forssa needs Kp 4 for the average oval edge to sit overhead. 215 of the 930 August days from 1996 to 2025 (23%) reached it in the GFZ Potsdam record, 7th of 12 months; storm days with Kp 5 or more made up 11%. Forssa sits at 58.6 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.
August across Finland
Forssa ranks 5th in Finland for civil night on August 15, behind Helsinki at 6.5 hours. Coming from July (2.4 hours at Forssa), August adds darkness, and the nights keep growing into September (9.5 hours on the 15th).
Darkness and moon, every night
| Night | Civil | Astronomical | Moon-free dark | Moon-free, 10 PM to 2 AM | Moon lit |
|---|---|---|---|---|---|
| Sun Aug 1 | 4 h 38 min | 0 min | 4 h 38 min | 2 h 47 min | 0% |
| Mon Aug 2 | 4 h 46 min | 0 min | 4 h 46 min | 2 h 51 min | 0% |
| Tue Aug 3 | 4 h 53 min | 0 min | 4 h 53 min | 2 h 54 min | 3% |
| Wed Aug 4 | 5 h | 0 min | 5 h | 2 h 58 min | 9% |
| Thu Aug 5 | 5 h 7 min | 0 min | 5 h 7 min | 3 h 2 min | 17% |
| Fri Aug 6 | 5 h 14 min | 0 min | 5 h 14 min | 3 h 5 min | 26% |
| Sat Aug 7 | 5 h 21 min | 0 min | 5 h 21 min | 3 h 9 min | 36% |
| Sun Aug 8 | 5 h 28 min | 0 min | 5 h 28 min | 3 h 13 min | 47% |
| Mon Aug 9 | 5 h 35 min | 0 min | 5 h 35 min | 3 h 16 min | 57% |
| Tue Aug 10 | 5 h 42 min | 0 min | 5 h 42 min | 3 h 20 min | 67% |
| Wed Aug 11 | 5 h 49 min | 0 min | 5 h 48 min | 3 h 22 min | 76% |
| Thu Aug 12 | 5 h 56 min | 0 min | 4 h 50 min | 2 h 21 min | 83% |
| Fri Aug 13 | 6 h 3 min | 0 min | 3 h 28 min | 56 min | 90% |
| Sat Aug 14 | 6 h 10 min | 0 min | 1 h 59 min | 0 min | 95% |
| Sun Aug 15 | 6 h 16 min | 0 min | 31 min | 0 min | 98% |
| Mon Aug 16 | 6 h 23 min | 0 min | 0 min | 0 min | 100% |
| Tue Aug 17 | 6 h 30 min | 0 min | 0 min | 0 min | 100% |
| Wed Aug 18 | 6 h 36 min | 0 min | 0 min | 0 min | 98% |
| Thu Aug 19 | 6 h 43 min | 0 min | 0 min | 0 min | 94% |
| Fri Aug 20 | 6 h 50 min | 0 min | 0 min | 0 min | 88% |
| Sat Aug 21 | 6 h 56 min | 0 min | 0 min | 0 min | 81% |
| Sun Aug 22 | 7 h 3 min | 0 min | 0 min | 0 min | 73% |
| Mon Aug 23 | 7 h 9 min | 0 min | 0 min | 0 min | 63% |
| Tue Aug 24 | 7 h 15 min | 0 min | 0 min | 0 min | 53% |
| Wed Aug 25 | 7 h 22 min | 41 min | 0 min | 0 min | 42% |
| Thu Aug 26 | 7 h 28 min | 1 h 22 min | 46 min | 30 min | 31% |
| Fri Aug 27 | 7 h 35 min | 1 h 49 min | 2 h 20 min | 2 h | 21% |
| Sat Aug 28 | 7 h 41 min | 2 h 10 min | 4 h 15 min | 3 h 51 min | 12% |
| Sun Aug 29 | 7 h 47 min | 2 h 29 min | 6 h 13 min | 4 h | 5% |
| Mon Aug 30 | 7 h 53 min | 2 h 45 min | 7 h 53 min | 4 h | 1% |
| Tue Aug 31 | 8 h | 3 h | 8 h | 4 h | 0% |
Questions
- Can you see the northern lights in Forssa in August?
- On dark, clear nights with enough activity. 31 of 31 nights at Forssa have civil darkness, and 23% of past August days reached Kp 4.
- How dark is Forssa in August?
- Forssa averages 6.4 hours of civil night a night in August 2027, from 4 h 38 min on the 1st to 8 h on the last night.
- How cloudy is Forssa in August?
- NASA POWER's 2001 to 2020 climatology gives Forssa's 1 degree cell 63% mean cloud in August, against 72% for the whole year. It is an all-hours average, not a forecast.
- What is the best night in August 2027 for aurora in Forssa?
- By darkness and moon alone, Aug 29, with 4 h of moon-free darkness inside 10 PM to 2 AM at Forssa. Activity on that date will only be known hours ahead.
- Is August or September better in Forssa?
- By civil night times the clear share, August scores 2.3 hours at Forssa and September 3.1. September 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.