When it comes to weather in Alaska, anything is possible — including snow in July.
According to Brian Brettschneider with our Ask a Climatologist segment, Alaska holds the North American record for most snow on a single day in July. Back in 1970 on July 19, it snowed 9.7 inches at the Summit weather station just south of Cantwell on the Parks Highway.
Brettschneider said 16 stations in Alaska have recorded snow in July.
Brian: To get snow in July, a lot of things have to come together, but it’s most likely to occur north of the Brooks Range. So Barrow, Utqiagvik, has recorded snow a number of days. To the west of there, Wainwright, Cape Lisburne, and east toward Kaktovik or Barter Island, also (have recorded) a number of snow days. Once you get south of the Brooks Range, the snow observations are all going to be at higher elevations. So places above 2,000 feet, so still uncommon, but not unheard of.
Annie: And what has to come together for it to snow in July?
Brian: Usually it’s going to be associated with an upper level low pressure system — the big L’s on the map. Not necessarily one of those Gulf of Alaska storms that’s moving in. It’s going to be something that’s packing its own cold air punch at several thousand feet up. And then when you get heavy precipitation, it can actually drag that cold air down, so often you see, it will be maybe 35 or 40 degrees and rain but as the precipitation intensity increases it will drag that cold air down and transition to snow. So it’s an uncommon event, but not unheard of.
Annie: How much snow are we talking?
Brian: Generally July snow events are light snow events. But there are a couple of instances where there have been greater than six inches. So back in 1976, up at Cape Lisburne, they had 7.2 inches of snow on July 4. And then at the Summit weather service office in July 1970, they had 9.7 inches on July 19. That’s not only an Alaska and United States record, that appears to be a North American record. In fact it’s so unusual that it’s been flagged by the National Center for Environmental Information as an outlier — that it’s probably bad data. But there was actually a weather service staffed person there to record it, so it almost certainly did actually occur.