Arctic freeze stills Lake McDonald

Bitterly cold air last week combined with a few calm nights to freeze over Lake McDonald in Glacier National Park — from stem to stern.

That hasn’t happened since 2007. Prior to that, the lake hadn’t froze over since 1997. Through the 1950s and 1960s, the nearly 10-mile long and 462-foot deep lake froze over an average of once every three years.

But with warmer winters, the lake hasn’t frozen over as often. Last week brought nearly ideal conditions, however.

First, an arctic front blew in with high winds and subzero temperatures. On Feb. 6, temperatures dipped to 22 below zero in West Glacier, but wind kept the ice from completely forming.

On Feb. 7, the temperature dropped to 20 below with calm conditions, and the lake froze over. Lows were in the single digits over the weekend and dropped to 6 below on Feb. 10.

People were ice-skating and skiing on Lake McDonald on Saturday and Sunday, but Park officials urge extreme caution — there are places where lake water is welling up through cracks onto the ice, and the ice is very thin in areas where springs and tributaries enter the lake.

Park spokeswoman Denise Germann said there was a report over the weekend of two skaters who broke through the ice but were able to get out on their own.

West Glacier wasn’t the coldest place in Glacier Park last week. The temperature in Polebridge dropped to a bone-chilling 34 below on Feb. 6. The temperature was 31 below at St. Mary the same day, according to the National Weather Service.

The cold air set a new record at Glacier Park International Airport on Feb. 6, reaching 23 below. The previous record for that day was 17 below, set in 1899.

Temperatures this week should moderate substantially, with highs in the 30s to near 40 today (Wednesday).