The US will shiver this week in a once-in-a-generation deep freeze, forecasters warn.
The most extreme arctic blasts, caused by a spinning pool of cold air known as the polar vortex, could bring temperatures as low as -46C (-50F).
Weather officials in the state of Iowa have warned people to “avoid taking deep breaths, and to minimise talking” if they do go outside.
States of emergency have been declared from Wisconsin down to Alabama.
John Gagan, a National Weather Service (NWS) meteorologist, said: “The intensity of this cold air, I would say, is once in a generation.”
The NWS is warning that frostbite is possible within just 10 minutes of being outside in such extreme temperatures.
The coldest temperatures are expected to hit on Wednesday, with forecasters predicting that Chicago will be colder than Antarctica.
The Illinois city could experience a low of -27F, with freezing winds making that feel closer to -50F, officials say.
What impact is the weather having?
Thousands of schools and businesses, predominantly in the Midwest, have been closed as have a number of government agencies.
Dozens of so-called warming centres – emergency shelters for those with nowhere to go – have been opened in Chicago and other cities across the US.
Chicago has also seen some more unusual consequences of the cold weather.
Police in the city are also reporting that people are being robbed of their expensive, designer, coats at gunpoint.
Those wearing Canada Goose jackets, which can cost as much as £900 ($1,100), have been targeted, CBS News reports.
Tickets to see the award-winning musical Hamilton are reportedly selling for half their usual value online, as theatre-goers avoid venturing out in the extreme conditions.
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