AN icy vortex of Arctic air pushed deadly wind chills and heavy snow into much of the US Midwest with meteorologists saying at least 32 states were in its path over the coming days as it moves south and east.
Even the northern tier of winter-hardy states and cities like Minnesota, Chicago and Milwaukee called off school for Monday as the country braced for wind chill temperatures down to minus 51 degrees Celsius and colder.
It was the first time in 17 years that Minnesota schools have been closed due to snow and dangerously low temperatures, reports said.
Governor Mark Dayton ordered the closings.
"Temperatures are deadly," warned Indianapolis Mayor Greg Ballard in broadcast remarks. Snow fell in his state of Indiana on Sunday at the rate of 5 centimetres an hour, media reports said.
In Green Bay, Wisconsin, tens of thousands of fans braved minus-26-degree wind chill temperatures to watch a key football playoff game between the Green Bay Packers and the San Francisco 49ers. Despite the Green Bay team having an apparent weather advantage, the 49ers won 23-20.
With the mercury expected to drop down to minus 44C through the night, food stands at Lambeau Field in Green Bay were offering free coffee and hot chocolate to keep fans warm. There were worries that beer would freeze in the open air stadium, CNN reported.
"Life-threatening wind chill," the National Weather Service warned.
"The coldest temperatures in almost two decades will spread into the northern and central US ... behind an Arctic cold front," the government forecaster said.
Before the "polar vortex" - as it's being called by meteorologists - hits the east and south, rain was expected to fall in those regions and be turned into thick ice when temperatures plunge into the minus-20C range on Tuesday.
The normally mild-temperature city of Nashville, Tennessee, has delayed by a day the post-holiday school start until Wednesday.
"Dangerously low temperatures forecast for Tuesday morning a concern for student safety," the school system said.
Flash freezes after the rain and blizzard conditions were expected from Tennessee to Missouri, Illinois, Indiana, Michigan, West Virginia, Ohio, Kentucky and Pennsylvania, the private forecaster AccuWeather said.
At least 13 people have died due to blizzard-like conditions and record cold over past days, most of them from traffic accidents in Michigan, Illinois, Kentucky and Indiana.
Broadcasters warned that frost bite could set in within just five minutes in the harsh conditions.
The weather caused cancellation of 3,467 flights and delays in another 11,191, according to the flight tracker FlightAware.com.
Overall, around 149 million people - about half the US population - were expected to be in the grip of the Arctic chill by Monday and Tuesday, meteorologists said.
