Aurora towns in Finland

Of the 65 indexed towns in Finland, 16 sit at 60 degrees geomagnetic or more, in or poleward of SWPC's 60 to 75 degree band, where no storm is needed; 49 sit between 55 and 60 degrees, where G1 (Kp 5) or less usually brings aurora into view.

On December 15 the median town gets 16.3 hours of civil night. Rovaniemi has the most at 17.7 hours and Raseborg the least at 16.0. 64 of these towns lose civil darkness altogether around the June solstice; Rovaniemi goes longest, 89 nights.

NASA POWER's 2001 to 2020 climatology puts median cloud amount in the dark months at 76%. Hämeenlinna is clearest at 74% and Lappeenranta cloudiest at 78%. These are all-hours averages for 1 degree cells, not forecasts.

Multiplying civil night by the clear share of the sky, March comes out best for 40 of the 65 towns and January for 20. SWPC notes a tendency toward larger storms near the equinoxes, which this score does not include.

The towns fall in 18 first-level regions. Uusimaa has 17, Pirkanmaa has 9, Southwest Finland has 8, Central Finland has 4. Regions with at least 5 indexed towns have their own page with three rankings.

• Uusimaa17 towns
• Pirkanmaa9 towns
• Southwest Finland8 towns
• Central Finland4 towns
• Kanta-Häme4 towns
• Kymenlaakso4 towns
• North Ostrobothnia4 towns
• North Savo4 towns
• Paijat-Hame4 towns
• Lapland3 towns
• Ostrobothnia3 towns
• South Ostrobothnia3 towns
• South Savo3 towns
• North Karelia2 towns
• Satakunta2 towns
• South Karelia2 towns
• Central Ostrobothnia1 towns
• Kainuu1 towns