Heinola · July 2027
Northern lights in Heinola in July 2027
Answer
July against the rest of the year
July cloud at Heinola averages 70% in NASA POWER's 2001 to 2020 record, 6 points clearer than its yearly mean. August is Heinola's clearest month at 67%. By civil night times clear sky, July scores 0.6 hours at Heinola, 11th of 12. Lahti, 32 km away, averages 64%, clearer by 6 points.
Civil night at Heinola starts July at 0 min and reaches 4 h 21 min by July 31 as the nights lengthen by 4.3 hours. 8 Heinola nights this month have no civil darkness at all. No night keeps the 10 PM to 2 AM window fully dark at Heinola. The sun never reaches 18 degrees down, so Heinola gets no astronomical night in July.
July night by night
July opens toward a new moon on Jul 4, with full moon on Jul 18, in Europe/Helsinki dates. Heinola gets 14 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: Jul 31 (2 h 48 min), Jul 15 (1 h 37 min), Jul 14 (1 h 32 min).
- 1
7% lit
no night
- 2
2% lit
no night
- 3
0% lit
no night
- 4
1% lit
no night
- 5
5% lit
no night
- 6
11% lit
no night
- 7
20% lit
no night
- 8
30% lit
no night
- 9
40% lit
0.3 h
- 10
51% lit
0.8 h
- 11
62% lit
1.1 h
- 12
71% lit
1.4 h
- 13
80% lit
1.6 h
- 14
87% lit
1.8 h
- 15
93% lit
2.0 h
- 16
97% lit
0.9 h
- 17
99% lit
0.0 h
- 18
100% lit
0.0 h
- 19
99% lit
0.0 h
- 20
96% lit
0.0 h
- 21
91% lit
0.0 h
- 22
85% lit
0.0 h
- 23
77% lit
0.0 h
- 24
68% lit
0.0 h
- 25
59% lit
0.0 h
- 26
48% lit
0.0 h
- 27
38% lit
0.0 h
- 28
27% lit
0.0 h
- 29
18% lit
0.1 h
- 30
10% lit
1.3 h
- 31
4% lit
3.2 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 Julys
Heinola needs Kp 4 for the average oval edge to sit overhead. 203 of the 930 July days from 1996 to 2025 (22%) reached it in the GFZ Potsdam record, 9th of 12 months; storm days with Kp 5 or more made up 9%. Heinola 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.
July across Finland
Heinola ranks 6th in Finland for civil night on July 15, behind Helsinki at 2.9 hours. Coming from June (0.0 hours at Heinola), July adds darkness, and the nights keep growing into August (6.2 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 Jul 1 | 0 min | 0 min | 0 min | 0 min | 7% |
| Fri Jul 2 | 0 min | 0 min | 0 min | 0 min | 2% |
| Sat Jul 3 | 0 min | 0 min | 0 min | 0 min | 0% |
| Sun Jul 4 | 0 min | 0 min | 0 min | 0 min | 1% |
| Mon Jul 5 | 0 min | 0 min | 0 min | 0 min | 5% |
| Tue Jul 6 | 0 min | 0 min | 0 min | 0 min | 11% |
| Wed Jul 7 | 0 min | 0 min | 0 min | 0 min | 20% |
| Thu Jul 8 | 0 min | 0 min | 0 min | 0 min | 30% |
| Fri Jul 9 | 16 min | 0 min | 16 min | 16 min | 40% |
| Sat Jul 10 | 48 min | 0 min | 48 min | 48 min | 51% |
| Sun Jul 11 | 1 h 7 min | 0 min | 1 h 7 min | 1 h 7 min | 62% |
| Mon Jul 12 | 1 h 22 min | 0 min | 1 h 22 min | 1 h 19 min | 71% |
| Tue Jul 13 | 1 h 36 min | 0 min | 1 h 36 min | 1 h 26 min | 80% |
| Wed Jul 14 | 1 h 48 min | 0 min | 1 h 48 min | 1 h 32 min | 87% |
| Thu Jul 15 | 1 h 59 min | 0 min | 1 h 59 min | 1 h 37 min | 93% |
| Fri Jul 16 | 2 h 10 min | 0 min | 54 min | 26 min | 97% |
| Sat Jul 17 | 2 h 20 min | 0 min | 0 min | 0 min | 99% |
| Sun Jul 18 | 2 h 30 min | 0 min | 0 min | 0 min | 100% |
| Mon Jul 19 | 2 h 39 min | 0 min | 0 min | 0 min | 99% |
| Tue Jul 20 | 2 h 49 min | 0 min | 0 min | 0 min | 96% |
| Wed Jul 21 | 2 h 58 min | 0 min | 0 min | 0 min | 91% |
| Thu Jul 22 | 3 h 7 min | 0 min | 0 min | 0 min | 85% |
| Fri Jul 23 | 3 h 15 min | 0 min | 0 min | 0 min | 77% |
| Sat Jul 24 | 3 h 24 min | 0 min | 0 min | 0 min | 68% |
| Sun Jul 25 | 3 h 32 min | 0 min | 0 min | 0 min | 59% |
| Mon Jul 26 | 3 h 41 min | 0 min | 0 min | 0 min | 48% |
| Tue Jul 27 | 3 h 49 min | 0 min | 0 min | 0 min | 38% |
| Wed Jul 28 | 3 h 57 min | 0 min | 0 min | 0 min | 27% |
| Thu Jul 29 | 4 h 5 min | 0 min | 5 min | 5 min | 18% |
| Fri Jul 30 | 4 h 13 min | 0 min | 1 h 20 min | 1 h 20 min | 10% |
| Sat Jul 31 | 4 h 21 min | 0 min | 3 h 13 min | 2 h 48 min | 4% |
Questions
- Can you see the northern lights in Heinola in July?
- On dark, clear nights with enough activity. 23 of 31 nights at Heinola have civil darkness, and 22% of past July days reached Kp 4.
- How dark is Heinola in July?
- Heinola averages 2.0 hours of civil night a night in July 2027, from 0 min on the 1st to 4 h 21 min on the last night.
- How cloudy is Heinola in July?
- NASA POWER's 2001 to 2020 climatology gives Heinola's 1 degree cell 70% mean cloud in July, against 76% for the whole year. It is an all-hours average, not a forecast.
- What is the best night in July 2027 for aurora in Heinola?
- By darkness and moon alone, Jul 31, with 2 h 48 min of moon-free darkness inside 10 PM to 2 AM at Heinola. Activity on that date will only be known hours ahead.
- Is July or August better in Heinola?
- By civil night times the clear share, July scores 0.6 hours at Heinola and August 2.0. August 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.