At least eight people have died in the US Midwest as the region shivers in the grip of its worst cold snap in decades.
An Iowa student found dead outside a college building is among victims of the deadly freeze.
Hospitals have been treating patients reporting frostbite as life across a swathe of the nation grinds to a halt.
The iciest blasts may still come on Thursday. Ninety million people – a third of the US – have seen temperatures of -17C (0F) or below.
Some 250 million Americans overall have experienced the “polar vortex” conditions, but southern states such as Florida have escaped the brutal chill.
Thursday could see America’s third largest city of Chicago breaking its 1985 record low of -32C (-25F), according to meteorologists.
The chill is drifting eastward on Thursday, bringing sub-zero temperatures to Northeastern cities such as Boston.
Areas downwind of the Great Lakes are expected to be buried by intense lake-effect snow lakes into Thursday night.