With a low of minus 27 degrees in Butte Thursday, the Berkeley Pit froze, giving life to the old saw "when hell freezes over."

Leeann Allegretto, National Weather Service meteorologist, said Thursday was the coldest day in a week that’s been the coldest Butte has seen so far this winter.

The high on Thursday reached 5 degrees right around 4 p.m.

Allegretto said from her Missoula office that temperatures will not rise much any time soon. The National Weather Service has issued a winter storm watch for Butte and other parts of Montana starting Friday afternoon and running through Saturday.

Butte and other parts of Montana could get blowing, drifting snow with wind gusts up to 45 miles per hour and dangerous wind chills.

Allegretto said Butte is not likely to get above freezing next week.

Temperatures could rise to the mid-20s in time for Valentine’s Day.

Gary Icopini, Bureau of Mines and Geology hydrogeologist, said Thursday that the chemistry hasn’t changed in the pit. The lake froze simply because it’s cold.

Last year the pit partially froze over. Mark Thompson, MR vice president for environmental engineering, said at the time that it was the first time in three years the pit had frozen.

Thompson said last year that the pit used to freeze over every winter in the 1990s, but by the 2000s, freezing on the toxic lake was “hit or miss.”

Icopini said it’s not as unusual as some might think. He said it partially froze earlier this winter in November of 2018.

Icopini said no one keeps records on when it freezes, but anecdotally, he’s noticed that when the fog disappears, that seems to be a sign that the toxic water has frozen.

He said the water is not warmer than a normal body of water, despite its unusual constituents of metals and sulfur. The pit water's depth reaches 800 to 900 feet.

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Nat'l Resources / General Reporter

Environmental and natural resources reporter for the Montana Standard.

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