After snow covered much of the United States on Monday, many Americans braced themselves for the coldest night in over two decades.

The arctic blast which is spreading south and towards the east is threatening lives, forcing businesses and schools to close and sending electricity and oil consumption soaring.

Medics are warning that the dangers of subzero temperatures go well beyond frost bite.

“So frostbite, obviously, we’re worried about skin: fingers, toes, ears, noses, that kind of thing. But being out in the cold temperature, letting the core temperature fall, can actually be life threatening; can stop one’s heart, it can stop one’s breathing, and lead to death,” warned Dr. Ryan fey of Hennepin County Medical Centre.

While officials in Chicago and many parts of the Midwest urged people to stay at home – emergency centres have been set up for the homeless.

The only source of heat at airports appears to be the fraying tempers with everyone going nowhere as thousands of flights are cancelled.