Northern lights in Lerwick: tonight’s chance

Sixty degrees north, on the wrong side of the pole

Lerwick lies at 60.2 degrees north, almost exactly the latitude of Whitehorse in the Yukon. In magnetic terms the two towns are far apart: Whitehorse is 5.4 degrees higher and needs about 2.7 Kp less, because the magnetic pole sits over the Canadian Arctic and the auroral oval leans toward North America. Shetland is therefore not under the oval on a quiet night, as northern Canada is, but it sits close enough to its edge that modest activity brings the aurora into view, low over the northern sea at first, then higher as the oval expands.

That geography also explains why Lerwick does better than the Scottish mainland. Every degree north counts on this side of the Atlantic, and the islands are the last land before open ocean. Looking north from the town, there is nothing but water and the rest of the Shetland archipelago between you and the oval.

Mirrie Dancers and the simmer dim

Shetland has its own words for both sides of the year. The Mirrie Dancers are the northern lights, and the simmer dim is the summer twilight that never quite becomes night. For aurora purposes the simmer dim means a long blank: from May to August the sun never sinks 18 degrees below the horizon. The season opens in late August and grows quickly, to 6.0 dark hours by mid-September and 11.5 by mid-November.

Waiting for the gap in the cloud

The Northern Isles sit in the path of North Atlantic depressions, and the cloud amount stays above 78% in every month of the NASA POWER record here. Showers on a northwest wind often leave clear intervals between them, which can last long enough for a display. Because Lerwick's own lights are small, a short walk or drive to a north facing shore or headland outside the town is usually enough to reach dark sky. Timing is generous in winter: on December 15 full darkness starts at 5:42 PM on UK clocks, so an evening display can be caught before dinner, and the Met Office aurora outlook gives a second opinion beside the SWPC Kp on nights that look promising. The UK page compares the rest of the country, and the Inverness page the Highland mainland.