The weather office in Des Moines, Iowa, where temperatures are expected to reach about -20C (-4F) , urged residents “to protect your lungs from severely cold air, avoid taking deep breaths; minimise talking.”
Midwest, and part of Chicago, could be colder than parts of Antarctica, said forecasters.
The frigid air is driven by a brief visit by the polar vortex, a whirling mass of cold air circulating in the mid to upper levels of the atmosphere every winter.
It usually stays closer to the poles but sometimes it breaks apart, sending chunks of Arctic air southward into the US during winter.
