Bitter cold dropped temperatures to record breaking lows in the Northeast on Friday.
The wind chill - what the temperature feels like - on the summit of Mount Washington, New Hampshire, dropped to minus 108 F.
That's likely the lowest wind chill ever recorded in the United States since meteorologists began calculating wind chills, said Brian Brettschneider, an Alaskan climate scientist.
Reconstructing wind chill based on historic records at Mount Washington shows the wind chill also could have been at minus 108 F or below on Jan. 22, 1885. The low that day - which still stands as the record low- was minus 50 F and the 24-hour average wind speed was 89 mph, Brettschneider said. That combination would produce a wind chill below minus 108 F, he said.
The temperature on Mount Washington dropped as low as minus 46 degrees F on Friday night, with 97 mph winds, the National Weather Service said.
Record daily lows were set in Boston, Massachusetts (minus 8 F), Providence, Rhode Island, (minus 4 F) and Bridgeport, Connecticut (2 F), the weather service said.
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Dangerously low wind chills
Elsewhere Friday night, the weather service reported an extreme wind chill of minus 62 F on Cadillac Mountain in Maine's Acadia National Park. Wind chills ranging from minus 31 F to minus 61 F were reported across at least five counties in Maine.
Wind chills below minus 32 F were also reported across much of New Hampshire.
The point of measuring wind chill is to help people understand the dangers of exposure to cold temperatures. The colder the air temperature and the higher the wind speed, up to a point, the colder it will feel.
What is wind chill? Understanding the wind chill index and how it's calculated
Wind chill is a concept pioneered by an Antarctica explorer and a polar scientist - Paul Siple and Charles Passel - in the 1940s. It was based on the length of time it took a vessel of near-freezing water to actually freeze under wind and temperature conditions.
The wind chill scale was modified in 2001, the weather service said, after a series of tests on volunteers who were placed in a chilled wind tunnel.
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What's causing the extreme cold?
A blast of Arctic air reached the region just as a rapid intensification of a storm system over the Canadian province of Newfoundland and Labrador churned up powerful wind, the Associated Press reported.
This article originally appeared on USA TODAY: Mount Washington wind chill: New Hampshire summit fell to minus 108 F