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IN PICTURES: Polar vortex grips America

A man takes a walk along the city's lakefront as temperature hung around -20 degrees in Chicago, Illinois. Businesses and schools have closed, Amtrak has suspended service into the city, more than a thousand flights have been cancelled and mail delivery has been suspended as the city copes with record-setting low temperatures.
A man takes a walk along the city's lakefront as temperature hung around -20 degrees in Chicago, Illinois. Businesses and schools have closed, Amtrak has suspended service into the city, more than a thousand flights have been cancelled and mail delivery has been suspended as the city copes with record-setting low temperatures.

The deep freeze gripping much of the US has been blamed on a polar vortex.Temperatures have plunged to as low as -30C in Chicago, which is colder than some parts of Antarctica.

A homeless man sits in the falling snow in the Financial District in New York City. The frigid air from the polar vortex in the Midwest will expand into the New York over the next few days. The city is under a wind chill advisory through Thursday morning, with possible win gusts up to 50 miles per hour.
A cyclist rides through the falling snow in the Financial District in New York City. The frigid air from the polar vortex in the Midwest will expand into the New York over the next few days. The city is under a wind chill advisory through Thursday morning, with possible win gusts up to 50 miles per hour.
Ice covers the Lake Michigan shoreline in Chicago, Illinois. Businesses and schools have closed, Amtrak has suspended service into the city, more than a thousand flights have been cancelled and mail delivery has been suspended as the city copes with record-setting low temperatures.
A man takes a walk along the city’s lakefront as temperature hung around -20 degrees in Chicago, Illinois. Businesses and schools have closed, Amtrak has suspended service into the city, more than a thousand flights have been cancelled and mail delivery has been suspended as the city copes with record-setting low temperatures.
A lone pedestrian crosses the Chicago River early Wednesday, A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures.
A warning sign is covered by ice at Clark Square park in Evanston. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures on Wednesday, triggering widespread closures of schools and businesses, and prompting the U.S. Postal Service to take the rare step of suspending mail delivery to a wide swath of the region.
Ice covers the Chicago River Wednesday in Chicago. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures triggering widespread closures of schools and businesses.
Ice is seen on the side of the Great Falls National Historic Park as a couple takes in the sights during a frigid winter day in Paterson, N.J. The cold snap followed a snowstorm and snow squalls are expected in the afternoon before temperatures continue to dip below the freezing point.
Drifting snow obscures a road near Mount Joy in Lancaster County. A bitter deep freeze is moving into the Northeast from the Midwest, sending temperatures plummeting and making road conditions dangerous.
A harbor light is covered with snow and ice on the Lake Michigan at 39th Street Harbor in Chicago. A deadly arctic deep freeze enveloped the Midwest with record-breaking temperatures on Wednesday.