Life-threatening conditions’: How severe will the Arctic storm in the US get?

Officials warned of "life-threatening" conditions as temperatures dropped as low as -50 degrees Fahrenheit in some areas. More than 4,000 flights planned for the Christmas weekend were canceled. The US National Weather Service (NWS) on Thursday warned of "dangerous cold" for much of the country, with a snow storm expected from late Thursday night into Friday morning.

The weather service warned that an Arctic blast would bring heavy snowfall to the Midwest, the Great Lakes and the Northeast through at least Saturday. This means that more than 200 million of the country's 335 million inhabitants will remain under varied weather advisories during the Christmas weekend, which is set to be the coldest the country has seen in decades.

Forecasters are expecting a bomb cyclone — when atmospheric pressure drops very quickly in a strong storm — to develop near the US-Canada border.

The NSW forecast that "record-breaking cold and life-threatening wind chills over the Great Plains [would] overspread the eastern half of the Nation by Friday." The weather agency warned that temperatures would drop between -40 to -70 degrees Fahrenheit (-40 to -56 degrees Celsius), with strong gusts and heavy snow expected to cause damage to infrastructure and disrupt travel. "Wind chills of this magnitude can cause frostbite in less than five minutes if precautions are not taken, with hypothermia and death also possible from prolonged exposure to the cold," it said. US President Joe Biden urged people across the country to take the weather warnings seriously. "This is not like a snow day when you are a kid," Biden warned Thursday after a briefing with federal officials. "This is serious stuff," he said.