Polar vortex
A polar vortex is an upper level low-pressure area lying near the Earth's poles.
There are two polar vortices in the Earth's atmosphere, overlying the North and South Poles
The United States has lowest temperatures due to a cold snap known as a polar vortex.
Temperatures fell to minus 30 degree Celsius in Chicago, colder than parts of Antarctica and minus 37 degree Celsius in North Dakota.
More than 1,600 flights have been cancelled at Chicago airport.
States of emergency have been declared in the Midwestern states of Wisconsin, Michigan and Illinois, and even in the normally warmer deep south states of Alabama and Mississippi.
The US Postal Service has called a halt to mail deliveries in parts of 10 states in the Great Plains and Midwest region.
Hundreds of schools, as well as colleges and universities, have been closed in the affected states
A polar vortex is an upper level low-pressure area lying near the Earth's poles.
There are two polar vortices in the Earth's atmosphere, overlying the North and South Poles
The United States has lowest temperatures due to a cold snap known as a polar vortex.
Temperatures fell to minus 30 degree Celsius in Chicago, colder than parts of Antarctica and minus 37 degree Celsius in North Dakota.
More than 1,600 flights have been cancelled at Chicago airport.
States of emergency have been declared in the Midwestern states of Wisconsin, Michigan and Illinois, and even in the normally warmer deep south states of Alabama and Mississippi.
The US Postal Service has called a halt to mail deliveries in parts of 10 states in the Great Plains and Midwest region.
Hundreds of schools, as well as colleges and universities, have been closed in the affected states
