Colder than Antarctica: brutal deep freeze grips US Midwest

A life-threatening deep freeze gripped the American Midwest on Wednesday as weather colder than Antarctica grounded flights, disrupted travel and brought life to a standstill for tens of millions.

Mail deliveries were suspended, schools and business closed, and residents encouraged to stay home in nearly a dozen states where temperatures overnight sank into the negative double digits, the worst cold to grip the region in a generation with all-time records still under threat.

America's third city Chicago -- where the morning temperature was -22 degrees Fahrenheit (-30 Celsius), which felt like -50 degrees (-46 Celsius) with wind chill -- was colder than Alaska's state capital and even colder than parts of Antarctica.

More than 1,500 flights were cancelled in the city's two major airports while rail operator Amtrak scrapped train services from its Chicago hub.

The US Postal Service -- known for its commitment to bringing the mail whatever the weather -- suspended deliveries in parts of .