Anchorage

Small market, and the three are genuinely distinct rather than variations. One of them uses a payment model that ought to be more common than it is.

That third arrangement is worth more than it looks in a place like Anchorage. Where the aurora is only visible on the more active nights, the biggest risk to a traveller is paying for an evening that was never going to work, and an operator willing to cancel rather than drive a full van into a hopeless sky has aligned its interests with yours. It is the equivalent of the money-back guarantees Finnish operators use, arrived at from the opposite direction.

North, in almost every case. The Glenn Highway runs up the Matanuska Valley past Palmer, with the Chugach mountains on one side and the Talkeetnas on the other, and within an hour of the city you are somewhere genuinely dark with an open northern horizon. The Knik River flats and the country around Hatcher Pass are the other regular destinations.

What the guides are solving for is the same everywhere in this business: a clear sky, no light, and nothing standing between you and the north. Anchorage makes the third of those harder than it sounds, because the city is hemmed in by mountains on the landward side, and a view north from the wrong spot is a view of a ridge. This is the main reason to buy a guided night rather than driving yourself, particularly on a first visit.

Two things decide how much aurora time a month contains: how often the sky is usable, and how many hours of real darkness there are to use it in. At 61°13′N the darkness column is shorter than anywhere else in this catalogue, which changes the answer.

Anchorage is the flattest North American row in our data and the answer is correspondingly soft: November, October and February are the best three, within a quarter of an hour of each other, with March close behind on the strength of the best cloud figure of the year at 49.4%.

December is the month to avoid, at 24.5% the weakest sky of the Anchorage year, and the one with the most darkness in it. It is also the reverse of Fairbanks, 570 km north, where December and January are the two best months. The two Alaskan bases do not share a season, which is worth knowing if you are combining them.

September is last, as it is everywhere, though by a narrower margin here than further north: 3.8 hours of darkness is the highest September figure of any destination we measure, because this is the southernmost base in the catalogue.

One limit, stated because it argues against the ranking: it measures how much dark clear sky a month contains, not the chance the aurora does something inside it. That caveat bites hardest here. At 61°13′N you also need the oval to expand south to reach you, and geomagnetic storms are close to twice as frequent around the equinoxes, which favours September and March. March in particular is probably better than its fourth place suggests.

Anchorage exists because of a railway. In 1915 a tent camp went up at the mouth of Ship Creek to build the line north to Fairbanks, and the camp became the city. It grew a second time because of geography that has nothing to do with Alaska: on a great-circle route, Anchorage is within about nine and a half hours' flying of most of the industrialised northern hemisphere, which turned its airport into one of the busiest cargo hubs on earth. That is why there are direct flights, and why an aurora trip to Alaska so often starts here whether or not it should.

The other date that shaped the place was 27 March 1964, when a magnitude 9.2 earthquake, the most powerful ever recorded in North America, struck 120 km east. Parts of the city slid into Cook Inlet. What stands today is largely what was rebuilt afterwards.