Is tonight a northern lights night?
Two things decide it: solar activity (the Kp index) and whether you can see the sky. We combine both into one number for all five places, so you can see where's best without picking one first.
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One email when the score for your place goes above 65. No newsletters, no spam.
How this score works
The score weighs three things: how active the sun is right now (the Kp index), whether the sky is clear (cloud cover), and how many hours of real darkness there are tonight. Kp measures geomagnetic activity worldwide, but Tromsø and the other places here sit almost directly under the aurora oval, so Kp 2 is often enough — it doesn't take a big storm. Cloud cover usually decides more than Kp does: a clear sky with Kp 2 beats a cloudy sky with Kp 5. Dark hours set the ceiling — no darkness, no visible aurora, whatever else looks good. It doesn't account for moonlight or local fog. Full detail, including the exact formula, is on the methodology page.
Some links on this page are affiliate links. The forecast is a planning aid, not a promise — nature does what it wants. How we calculate this →
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