AKIPRESS.COM - Cities are all but shutting down across the US Midwest as the region shivers in a deadly cold snap known as a polar vortex, BBC reports.

At least seven people have been killed in several states as a result of the arctic weather.

Temperatures fell to -30C (-22F) in Chicago - colder than parts of Antarctica - and -37C in North Dakota.

Freezing weather will chill 250 million Americans, and 90 million will experience -17C (0F) or below.

Farmers across the Midwest have been taking measures to protect their livestock, including building igloos for chickens.

Animal rights organisation Peta has warned people to bring pets indoors.

Residents of America's third largest city are no strangers to perishing cold, but they have been warned to expect an unusually dangerous freeze.