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At least 15 people are believed to have died across the US as a result of the cold blast, which has crippled much of the country. According to the latest official figures, 187 million people have been affected by the severe weather.

Across the country, wind chill warnings were in place for 32 states from Montana in the north to Florida in the south east.

School closures were reported from as far afield as Minneapolis and Chicago in the north to Atlanta and northern Florida in the south.

The eastern seaboard, which had escaped the initial impact of the polar vortex, was also affected. Andrew Cuomo, the governor of New York state, closed swathes of the state highways as a precaution.

In Illinois, the governor, Pat Quinn, declared a state of emergency as the state wrestled with the most severe temperatures in two decades. It was so cold that water thrown into the air turned into ice before landing on the ground.

In Iowa, Tom Rauen became an internet sensation when he posted a film on YouTube showing a wet T-shirt turning into ice in a minute.

“I thought it would be cool if I could shape it into what it would look like if someone was wearing it,” he said. “I left it standing up on the sidewalk for a while and when I brought it inside there was a little tear in it – just from it freezing, it had become it very brittle. I took the tear and just ripped the T-shirt in half like it was a piece of paper. It was crazy.”

The cold weather in the South triggered fears that the Florida citrus crop could be hit. America’s transport system continued to be affected. In Illinois, more than 500 passengers were stuck on three Amtrak trains overnight after they were trapped by the snow. Thousands of flights cancelled across the country.

Temperatures are expected to climb slowly by the end of the week.