The best month.

Clearest dark skies in September

Top three: Fort McMurray, Yellowknife, Ilulissat. 36 watch points with at least one night of an hour's astronomical darkness this month, ranked by clear sky (100 − mean cloud cover); dark hours are the mean over the month's dark nights, and a part-dark month says when its darkness starts or ends. Cloud is only one of the three conditions — a clear Kp 9 spot is almost never lit; the threshold shown is each spot's own.

1. Watch pointcleardarkglow
2. 01Fort McMurray North America · N41%6.7hKp 3+
3. 02Yellowknife North America · N34%5.3hKp 1+
4. 03Ilulissat Greenland · N· dark from 16 Sep33%4hKp 0+
5. 04Whitehorse North America · N31%5.9hKp 3+
6. 05Nuuk Greenland · N· dark from 3 Sep30%4.9hKp 1+
7. 06Oulu Northern Europe · N· dark from 5 Sep29%4.7hKp 3+
8. 07Kangerlussuaq Greenland · N· dark from 10 Sep29%4.4hKp 0+
9. 08Dawson City North America · N· dark from 2 Sep28%4.8hKp 1+
10. 09Fairbanks North America · N· dark from 4 Sep28%4.7hKp 1+
11. 10Lofoten Islands Northern Europe · N· dark from 13 Sep27%4.1hKp 1+
12. 11Svolvær Northern Europe · N· dark from 13 Sep26%4.1hKp 2+
13. 12Anchorage North America · N25%5.7hKp 3+
14. 13Coldfoot / Bettles North America · N· dark from 11 Sep25%4.4hKp 0+
15. 14Churchill North America · N24%6.3hKp 1+
16. 15Rovaniemi Northern Europe · N· dark from 9 Sep24%4.5hKp 2+
17. 16Reykjavík Northern Europe · N· dark from 3 Sep23%4.9hKp 2+
18. 17Kiruna Northern Europe · N· dark from 12 Sep23%4.2hKp 2+
19. 18Senja Northern Europe · N· dark from 16 Sep23%3.9hKp 1+
20. 19Nellim Northern Europe · N· dark from 15 Sep22%4.1hKp 2+
21. 20Ivalo Northern Europe · N· dark from 14 Sep22%4hKp 2+
22. 21Kirkenes Northern Europe · N· dark from 17 Sep22%3.8hKp 1+
23. 22Faroe Islands (Tórshavn) Northern Europe · N21%5.5hKp 3+
24. 23Inari Northern Europe · N· dark from 15 Sep21%4hKp 1+
25. 24Tromsø Northern Europe · N· dark from 17 Sep21%3.9hKp 1+
26. 25Iqaluit North America · N20%4.8hKp 1+
27. 26Murmansk / Kola Peninsula Northern Europe · N· dark from 15 Sep20%4hKp 2+
28. 27Lyngen Northern Europe · N· dark from 17 Sep20%3.9hKp 1+
29. 28Alta Northern Europe · N· dark from 18 Sep20%3.8hKp 1+
30. 29Denali North America · N19%5.1hKp 2+
31. 30Akureyri Northern Europe · N· dark from 7 Sep19%4.7hKp 1+
32. 31Saariselkä Northern Europe · N· dark from 14 Sep19%4.2hKp 2+
33. 32Abisko Northern Europe · N· dark from 14 Sep17%4.2hKp 1+
34. 33Skibotn Northern Europe · N· dark from 16 Sep17%3.9hKp 1+
35. 34Iceland (countrywide) Northern Europe · N· dark from 4 Sep15%4.8hKp 2+
36. 35Kilpisjärvi Northern Europe · N· dark from 16 Sep13%4.1hKp 1+
37. 36Utqiaġvik (Barrow) North America · N· dark from 21 Sep11%3.4hKp 0+

No true darkness in September

No night this month reaches an hour of astronomical darkness — clear or not, the aurora is not visible. Their cloud figures are shown for the record.

Cloud: Open-Meteo Historical Weather API (ERA5 reanalysis), cloud_cover_mean (daily), averaged by calendar month, 2015–2024. Climatology, not a forecast — a regional ~25 km grid; local microclimates (a valley's "blue hole") are not captured. Darkness: astronomical (sun below −18°) computed for the 15th of the month at each spot. Night-by-night darkness & moon → Season sheet (PDF) → Plan the trip →