Northern lights in Inverness: tonight’s chance

At the head of the Moray Firth

Inverness grew where the River Ness meets the sea, at the inner end of the Moray Firth, and its geography is unusually helpful for an aurora town. The firth runs northeast toward the open North Sea, and across the narrow water the Black Isle rises low and largely rural. From the northern edge of the city, or from the shore on the far side of the Kessock Bridge, the northern sky opens over farmland and water rather than streets. Loch Ness lies the other way, down the Great Glen to the southwest, and its steep sides make it a poor place to look north.

Where the threshold and the overhead line meet

Inverness sits in the narrow band of magnetic latitude where the Kp needed to see aurora and the Kp that brings the oval edge overhead coincide, about 5.5. For a watcher this means a minor storm can paint a large part of the sky, while a forecast below that level usually shows nothing. Lerwick, 2.9 degrees farther north in magnetic latitude, needs about 1.5 Kp less; Edinburgh needs about 0.9 Kp more. On the scale of Britain, Inverness is the point where aurora watching shifts from an occasional event to a regular winter possibility.

Driving north improves the odds only slowly. Thurso, on the Caithness coast, gains 1.3 degrees of magnetic latitude and lowers the threshold by 0.6 Kp, a real but modest gain for a long trip. The bigger reward of the north coast is the horizon: the sea to the north, and almost no artificial light between you and Orkney.

Highland weather in the dark months

The Highlands catch Atlantic fronts head on, but Inverness lies on the drier eastern side, in the lee of the mountains, and clear intervals are more frequent here than on the west coast. In winter, northerly winds can bring showers off the sea with clear gaps between them, and a calm high pressure spell brings frost and steady, open skies. July is the cloudiest month here, but it falls in the summer gap anyway. In the dark season the figures are close from month to month, so the nights to pick are the ones the forecast shows clear. The Lerwick page covers Shetland, and the Aberdeen page the east coast.