Skip to content
ERA5 climatology · 2015–2024
When to go

The best month.

Pick a month and every watch point is ranked by its real monthly cloud cover — 2015–2024 reanalysis means, lower is better — with the spots that have no true darkness that month set apart. Or pick a spot for its twelve-month chart.

Clear sky by month · Tromsø100 − mean cloud cover · higher is better

Clearest dark months here (outlined): Jan, Mar, Oct. Faint: no night with an hour of astronomical darkness — midnight sun (Jun, Jul); white nights, twilight only (Apr, May, Aug). Part-faint months are dark on some nights only: dark until 24 Mar; dark from 17 Sep. ERA5 reanalysis, 2015–2024 monthly mean. Climatology, not a forecast — a regional ~25 km grid; local microclimates are not captured. Darkness & moon calendar → Best month, all spots →

● Tonight at Tromsø — live →

Clearest dark skies in May

The aurora belt · Kp 3 or lessAll 70 spots

Top three: South Africa (Cape Point / Hermanus), North Dakota, Copenhagen. 28 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. 01South Africa (Cape Point / Hermanus) Africa · S48%10.8hKp 9+
  2. 02North Dakota North America · N45%3.9hKp 5+
  3. 03Copenhagen Northern Europe · N· dark until 3 May45%1.6hKp 5+
  4. 04Christchurch Oceania · S44%11.1hKp 6+
  5. 05South Australia coast (Kangaroo Is.) Oceania · S44%10.8hKp 7+
  6. 06Launceston Oceania · S42%11hKp 5+
  7. 07Dunedin / Otago Peninsula Oceania · S41%11.1hKp 5+
  8. 08Lake Tekapo (Aoraki Mackenzie) Oceania · S41%11.1hKp 5+
  9. 09Michigan Upper Peninsula (Keweenaw) North America · N41%4.2hKp 5+
  10. 10Edmonton North America · N· dark until 11 May41%2.3hKp 4+
  11. 11Hobart Oceania · S39%11hKp 5+
  12. 12Victoria coast (Phillip Island) Oceania · S39%10.9hKp 6+
  13. 13Northern Minnesota (Voyageurs) North America · N39%3.8hKp 5+
  14. 14Jasper North America · N· dark until 14 May38%2.5hKp 4+
  15. 15Montana (Glacier NP) North America · N36%3.5hKp 5+
  16. 16Northern Maine (Acadia) North America · N35%4.5hKp 5+
  17. 17Patagonia (El Calafate) South America · S34%11.3hKp 9+
  18. 18Washington (North Cascades) North America · N34%3.5hKp 6+
  19. 19Bruny Island / Cockle Creek Oceania · S30%11.1hKp 4+
  20. 20Invercargill Oceania · S29%11.1hKp 5+
  21. 21Edinburgh Northern Europe · N· dark until 2 May29%1.4hKp 5+
  22. 22Punta Arenas South America · S28%11.4hKp 9+
  23. 23Donegal Northern Europe · N· dark until 7 May27%1.9hKp 5+
  24. 24Falkland Islands South Atlantic · S26%11.3hKp 9+
  25. 25Queenstown / Southland Oceania · S23%11.1hKp 5+
  26. 26Stewart Island / Rakiura Oceania · S21%11.2hKp 4+
  27. 27Ushuaia / Tierra del Fuego South America · S20%11.4hKp 8+
  28. 28South Georgia South Atlantic · S8%11.4hKp 8+
clear = 100 − mean cloud cover · dark = mean hours of astronomical dark · glow = the spot's Kp for a glow

No true darkness in May

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 →