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 -53C (-64F).
Weather officials in the state of Iowa have warned people to “avoid taking deep breaths, and to minimise talking” if they go outside.
At least 55 million people are forecast to experience sub-zero temperatures.
A state of emergency has been declared in the Midwestern states of Wisconsin, Michigan and Illinois as well as in the normally more clement southern states of Alabama and Mississippi.
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.
