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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 · Rovaniemi100 − mean cloud cover · higher is better

Clearest dark months here (outlined): Mar, Sep, Oct. Faint: no night with an hour of astronomical darkness — midnight sun (Jun); white nights, twilight only (May, Jul, Aug). Part-faint months are dark on some nights only: dark until 2 Apr; dark from 9 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 Rovaniemi — live →

Clearest dark skies in August

The aurora belt · Kp 3 or lessAll 70 spots

Top three: Fort McMurray, Yellowknife, Churchill. 7 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. 01Fort McMurray North America · N· dark from 12 Aug44%3.5hKp 3+
  2. 02Yellowknife North America · N· dark from 29 Aug41%1.8hKp 1+
  3. 03Churchill North America · N· dark from 18 Aug33%3hKp 1+
  4. 04Whitehorse North America · N· dark from 24 Aug32%2.5hKp 3+
  5. 05Anchorage North America · N· dark from 25 Aug29%2.2hKp 3+
  6. 06Faroe Islands (Tórshavn) Northern Europe · N· dark from 28 Aug22%2.1hKp 3+
  7. 07Denali North America · N· dark from 31 Aug13%1.6hKp 2+
clear = 100 − mean cloud cover · dark = mean hours of astronomical dark · glow = the spot's Kp for a glow

No true darkness in August

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.

Midnight sun — the sun never sets

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 →