A deadly chill has much of the United States and Canada in its wintry grip, as a record-breaking cold snap brought temperatures lower than on the surface of Mars.
It was so cold in Chicago that the polar bear at the Lincoln Park zoo – who admittedly had not built up the winter fat stores of her wild cousins – was brought inside to warm up.
And in Kentucky, an escaped inmate begged to be let back into prison so he could warm up after spending the night shivering in an abandoned house.
All of Canada and all the US states bar tropical Hawaii recorded temperatures below freezing yesterday, even usually sunny and warm Florida and California.
But the most dangerous cold – cold that can cause frostbite in a minute and death in a matter of hours – hit the Midwest, dragged down as the 'polar vortex' brought frigid air from the Arctic. Schools, businesses and government offices were closed. Water mains and household pipes froze. Airplanes were grounded, trains were halted and roads and pavements became ice rinks.
The town of Embarrass, Minnesota, recorded the lowest temperature in the United States at -37 degrees Centigrade.
The Mars Rover has been sending back daily temperature readings from its tour of the Red Planet ranging from -25 to -31 degrees Celsius (-13 and -24 degrees Fahrenheit).