Aurora towns ranked by dark season length

The widest gap between neighbours falls between Buffalo and Anchorage, 75 days. 4 neighbouring pairs sit within 3 days of each other (Seattle and Minneapolis; Minneapolis and Duluth; Duluth and Portland, Maine), close enough that their order means little.

The five lower 48 towns tie at the top: every day of the year has at least 4 hours of evening civil night. The far-north towns each lose part of the year, from about two and a half months at Anchorage to about four at Tromsø. Their order follows map latitude, since the season ends when summer nights grow too short.

A long season is not the same as frequent aurora. The lower 48 towns have dark evenings all year but sit far from the oval; the far-north towns sit near or under it but lose the summer. Read this ranking beside the geomagnetic one before choosing a town or a month.

How to use it. The dark season sets the calendar: outside it, a far-north trip usually fails on light alone, as SWPC's summer caveat says. Inside it, pick dates with the equinox and the moon in mind. The ranking uses Glow's 4 evening hour bar. If shorter nights are fine for you, the aurora season finder draws the full-year ribbon so you can apply your own cutoff.

Limits. The 4 hour bar and the 18:00 to 06:00 frame are Glow's own choices, stated so the numbers can be checked. A different bar would move every far-north town's season dates by days or weeks. The year scan samples the sun every 15 minutes and interpolates each crossing, so a night that sits right at the bar can fall either side of it.

The order does not follow the map. Minneapolis ranks above Duluth although it sits farther south on the map; Buffalo ranks above Anchorage although it sits farther south on the map; Anchorage ranks above Yellowknife although it sits farther south on the map.

SWPC warns that the high latitudes where aurora occurs do not get dark in summer. This ranking shows how long each town's usable season lasts before the light returns.

Glow scans every day of the year at 15 minute steps and counts days with at least 4 hours of civil night between 18:00 and 06:00 local time. That 4 hour bar is Glow's own definition, matching the length of SWPC's 10 PM to 2 AM window. The note gives the run of nights with no civil darkness at all.

For your own coordinates, use the aurora season finder. The background is in when is it too light for the aurora?, and every threshold is listed on the methodology page.