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ERA5 climatology · 2015–2024
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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 · Anchorage100 − mean cloud cover · higher is better

Clearest dark months here (outlined): Mar, Apr, Nov. Faint: no night with an hour of astronomical darkness — white nights, twilight only (May, Jun, Jul). Part-faint months are dark on some nights only: dark until 16 Apr; dark from 25 Aug. 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 Anchorage — live →

Clearest dark skies in September

The aurora belt · Kp 3 or lessAll 70 spots

Top three: North Dakota, South Africa (Cape Point / Hermanus), Montana (Glacier NP). 72 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. 01North Dakota North America · N55%7.9hKp 5+
  2. 02South Africa (Cape Point / Hermanus) Africa · S50%9.3hKp 9+
  3. 03Montana (Glacier NP) North America · N49%7.8hKp 5+
  4. 04South Australia coast (Kangaroo Is.) Oceania · S47%9.3hKp 7+
  5. 05Michigan Upper Peninsula (Keweenaw) North America · N47%8hKp 5+
  6. 06Northern Maine (Acadia) North America · N46%8.1hKp 5+
  7. 07Edmonton North America · N45%7.2hKp 4+
  8. 08Christchurch Oceania · S44%9hKp 6+
  9. 09Northern Minnesota (Voyageurs) North America · N43%7.9hKp 5+
  10. 10Lake Tekapo (Aoraki Mackenzie) Oceania · S42%8.9hKp 5+
  11. 11Fort McMurray North America · N41%6.7hKp 3+
  12. 12Patagonia (El Calafate) South America · S40%8.6hKp 9+
  13. 13Washington (North Cascades) North America · N40%7.8hKp 6+
  14. 14Victoria coast (Phillip Island) Oceania · S39%9.2hKp 6+
  15. 15Launceston Oceania · S39%9.1hKp 5+
  16. 16Dunedin / Otago Peninsula Oceania · S39%8.8hKp 5+
  17. 17Copenhagen Northern Europe · N39%6.9hKp 5+
  18. 18Hobart Oceania · S38%9hKp 5+
  19. 19Estonia (Tartu / coast) Northern Europe · N36%6.4hKp 5+
  20. 20Stockholm Northern Europe · N36%6.2hKp 4+
  21. 21Jasper North America · N35%7.3hKp 4+
  22. 22Oslo Northern Europe · N34%6.1hKp 4+
  23. 23Helsinki Northern Europe · N34%6hKp 4+
  24. 24Yellowknife North America · N34%5.3hKp 1+
  25. 25Ilulissat Greenland · N· dark from 16 Sep33%4hKp 0+
  26. 26Bruny Island / Cockle Creek Oceania · S32%9hKp 4+
  27. 27Falkland Islands South Atlantic · S32%8.5hKp 9+
  28. 28Edinburgh Northern Europe · N31%6.9hKp 5+
  29. 29Aberdeenshire Northern Europe · N31%6.7hKp 5+
  30. 30Whitehorse North America · N31%5.9hKp 3+
  31. 31Invercargill Oceania · S30%8.8hKp 5+
  32. 32Punta Arenas South America · S30%8.3hKp 9+
  33. 33Nuuk Greenland · N· dark from 3 Sep30%4.9hKp 1+
  34. 34Oulu Northern Europe · N· dark from 5 Sep29%4.7hKp 3+
  35. 35Kangerlussuaq Greenland · N· dark from 10 Sep29%4.4hKp 0+
  36. 36Dawson City North America · N· dark from 2 Sep28%4.8hKp 1+
  37. 37Fairbanks North America · N· dark from 4 Sep28%4.7hKp 1+
  38. 38Orkney Northern Europe · N27%6.3hKp 5+
  39. 39Lofoten Islands Northern Europe · N· dark from 13 Sep27%4.1hKp 1+
  40. 40Queenstown / Southland Oceania · S26%8.9hKp 5+
  41. 41Svolvær Northern Europe · N· dark from 13 Sep26%4.1hKp 2+
  42. 42Caithness (north Highlands) Northern Europe · N25%6.4hKp 5+
  43. 43Anchorage North America · N25%5.7hKp 3+
  44. 44Coldfoot / Bettles North America · N· dark from 11 Sep25%4.4hKp 0+
  45. 45Stewart Island / Rakiura Oceania · S24%8.8hKp 4+
  46. 46Ushuaia / Tierra del Fuego South America · S24%8.2hKp 8+
  47. 47Donegal Northern Europe · N24%7.1hKp 5+
  48. 48Churchill North America · N24%6.3hKp 1+
  49. 49Shetland Northern Europe · N24%5.9hKp 4+
  50. 50Rovaniemi Northern Europe · N· dark from 9 Sep24%4.5hKp 2+
  51. 51Reykjavík Northern Europe · N· dark from 3 Sep23%4.9hKp 2+
  52. 52Kiruna Northern Europe · N· dark from 12 Sep23%4.2hKp 2+
  53. 53Senja Northern Europe · N· dark from 16 Sep23%3.9hKp 1+
  54. 54Nellim Northern Europe · N· dark from 15 Sep22%4.1hKp 2+
  55. 55Ivalo Northern Europe · N· dark from 14 Sep22%4hKp 2+
  56. 56Kirkenes Northern Europe · N· dark from 17 Sep22%3.8hKp 1+
  57. 57Faroe Islands (Tórshavn) Northern Europe · N21%5.5hKp 3+
  58. 58Inari Northern Europe · N· dark from 15 Sep21%4hKp 1+
  59. 59Tromsø Northern Europe · N· dark from 17 Sep21%3.9hKp 1+
  60. 60Iqaluit North America · N20%4.8hKp 1+
  61. 61Murmansk / Kola Peninsula Northern Europe · N· dark from 15 Sep20%4hKp 2+
  62. 62Lyngen Northern Europe · N· dark from 17 Sep20%3.9hKp 1+
  63. 63Alta Northern Europe · N· dark from 18 Sep20%3.8hKp 1+
  64. 64Denali North America · N19%5.1hKp 2+
  65. 65Akureyri Northern Europe · N· dark from 7 Sep19%4.7hKp 1+
  66. 66Saariselkä Northern Europe · N· dark from 14 Sep19%4.2hKp 2+
  67. 67Abisko Northern Europe · N· dark from 14 Sep17%4.2hKp 1+
  68. 68Skibotn Northern Europe · N· dark from 16 Sep17%3.9hKp 1+
  69. 69Iceland (countrywide) Northern Europe · N· dark from 4 Sep15%4.8hKp 2+
  70. 70Kilpisjärvi Northern Europe · N· dark from 16 Sep13%4.1hKp 1+
  71. 71Utqiaġvik (Barrow) North America · N· dark from 21 Sep11%3.4hKp 0+
  72. 72South Georgia South Atlantic · S10%8.2hKp 8+
clear = 100 − mean cloud cover · dark = mean hours of astronomical dark · glow = the spot's Kp for a glow

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.

White nights — twilight only

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 →