NEW YORK - Millions of people across the United States on Monday made last minute preparations for an unusually bitter Arctic blast that could send temperatures plummeting to their coldest in 20 years.
The northeastern United States and parts of Canada have endured heavy snow and deadly sub-zero conditions since the start of the year, but the deep freeze is now moving through the midwestern United States and threatening usually balmy areas further south like Tennessee and Alabama.
The wind chill from the rare "polar vortex" could make it feel as cold as -60 Fahrenheit (-51 Celsius) in places, weather forecasters say, prompting authorities in several towns and cities to issue warnings that people should stay indoors and stock up on food.
Exposed skin could suffer frostbite in as little as five minutes in such conditions, experts warn.
The National Weather Service described the weather as "life-threatening."
"The coldest temperatures in almost two decades will spread into the northern and central US today behind an Arctic cold front," it said.
"Combined with gusty winds, these temperatures will result in life-threatening wind-chill values as low as 60 degrees (Fahrenheit) below zero.
Also, heavy snow will develop from the eastern Plains to the Great Lakes today, with up to a foot of accumulation possible."
Authorities warning people that they could face issues like cars that won't start and flooded roads that quickly ice over caused by water pipes that freeze and burst.
Thousands of flights out of major airports like Chicago O'Hare International and New York's John F. Kennedy were delayed or canceled Sunday due to weather-related problems.
At O'Hare, one of the country's busiest airports, officials said that more than 1,300 flights were canceled.