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Denver sees record-breaking 37-degree temperature drop in a single hour

Only two days old, winter showed its fury across Colorado on Wednesday and Thursday — fury that's quickly spreading south and east.

DENVER (CN) — A arctic cold front swept through Denver on Wednesday afternoon, driving temperatures down an astounding 75 degrees over an 18-hour period and setting a new record for greatest temperature decrease in a single hour — from 42 degrees to 5 degrees.

The data was collected by the Automated Surface Observing Systems program, or ASOS, at the Denver International Airport. The National Weather Service has more than 900 ASOS sites across the country with data going back to the 1970s.

The 75-degree drop nearly touched the previous 18-hour temperature swing record of 76 degrees recorded on Dec. 14, 2008.

Denver International Airport canceled more than 460 flights, according to FlightAware, with only Chicago O'Hare reporting more cancellations in the U.S.

The cold snap came courtesy of northwestern Canada, where a clockwise-rotating anticyclone built up high pressure, pushing frigid arctic air south across the U.S., gifting winter weather down Colorado’s Front Range, across Texas and out to the Gulf of Mexico.

“This is a fairly rare event,” said Jeff Weber, an atmospheric scientist at the National Center for Atmospheric Research. “This is like a once in every 30 years event, we haven't seen temperatures this cold since 1990, so this is unusual, but it's not unheard of.”

Since 1990, more than 1 million newcomers moved to Denver metro area and the population of Colorado nearly doubled, from 3.2 million to 5.8 million as of 2020. Most moved from Texas, California and Florida, per Stacker's analysis of U.S. Census data, and have likely never experienced extreme winter conditions.

“We've had a large amount of our population come to Colorado since 2000s," Weber said. "For them, this is a record-breaking snow and cold event.”

The storm threatened other records as well. Temperatures at Denver International Airport hit minus 24 degrees Thursday morning, just shy of the monthly record of 25 degrees below zero set on Dec. 22, 1990.

Though not record-shattering, the polar plunge moniker is warranted, with life-threatening temperatures reported around the state. The eastern plains and foothills experienced chilling temperatures between 10 and 15 below zero.

Still, the Denver Police Department confirmed Thursday morning that no weather-related deaths had been reported. That may be due to advance notice given by the National Weather Service allowing people to prepare for the bitter cold.

“We noticed the trend almost seven days in advance,” said Greg Heavener, warning coordination meteorologist at the National Weather Service in Boulder. “Realizing that we were looking at a life-threatening situation when it when it came to the wind chill, we were able to work with our local media partners in the Denver Metro area, really pushing messaging out there of how extreme this event was going to be.”

Wind chill readings ranged from minus 35 to minus 50 degrees across the eastern plains and from minus 25 to minus 35 in the metro areas of Denver and Boulder. Denver's wind chill record is minus 45 degrees.

In anticipation of the extreme weather, Denver Mayor Michael Hancock announced the opening of the Denver Coliseum to serve as a 24-hour warming center and Colorado Governor Jared Polis activated 100 members of the National Guard “to support extreme cold weather operations.”

The state Supreme Court and Court of Appeals closed Thursday in anticipation of the cold, along with several district courts around the state.

Denver's last sub-zero high was in 2014. The area hasn't seen temperatures lower than 20 degrees below zero since 1990. In December, the Mile High City's average high temperature is 44 degrees, with an average low of 18.

The coldest temperature ever recorded in Denver was minus 29 degrees on Jan. 9, 1875. Temperatures of 25 degrees below zero were recorded in 1876 and four times in the 20th century.

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