Record: New York's Central Park hits 22 C, the warmest Christmas Eve since 19th century

US citizens on the East Coast shed their Christmas sweaters on Thursday to enjoy soaring temperatures ahead of the holiday, as further south deadly tornadoes cut a swathe of destruction through rural communities.

According to the US National Weather Service, temperatures in New York's iconic Central Park peaked at 22 C, the warmest Christmas Eve since records began in 1871.

In the capital, tourists and last minute shoppers wore T-shirts and sat outside at sidewalk cafes as federal workers left their offices dressed for holiday parties.

High temperatures were reported as far north as Saint Anicet in the Canadian province of Quebec, which hit 21 C, and the NWS reported that the port of Norfolk in Virginia broke its all time December record of 28 C.

At Maryland's only ski station just one of 35 trails was open, thanks to artificial snow-making machines. Last year the Wisp Resort's runs opened on Dec 13, NBC Washington reported.

But the abnormally balmy temperatures had tragic consequences in weather further south, where more than a dozen tornadoes were reported in six states.

At least 14 people were killed as the storms, feeding on the unseasonable warm air, left a trail of destruction from Illinois to Alabama.

Heavy damage was inflicted in the south, causing seven deaths in Mississippi alone, according to the state's Emergency Management Agency.

A seven-year-old boy was found dead after the storm picked up and tossed the car he was traveling in, fire chief Kenny Holbrook told reporters in the town of Holly Springs, where some 5,000 customers were still believed to be without power.

Violent storm

At least 40 people were injured in the state, Governor Phil Bryant said, as he issued a state of emergency that will allow local governments to request aid for recovery.

"Most of these storms caused a lot of damage in north Mississippi but our teams are out assessing the damage, trying to put a quantity on how many homes and how many businesses have been damaged," the emergency agency's Brett Carr said.

The Tennessee Emergency Management Agency said six people were killed in the state, while media reported one fatality in the state of Arkansas.

The National Weather Service in Memphis, Tennessee, said that an "exceptionally long-track, violent tornado" had likely traveled all the way from Mississippi to Tennessee.

"If it is continuous it would be the longest track DEC tornado on record here in the Mid-South," the agency posted on Twitter.

One Perry County survivor told CNN that after the tornado it looked "like a waste land. There's nothing left".

"We were in the house. We heard the wind picking up. We dashed to the storm shelter. We had 45 seconds and it hit," he said.

A man in a T-shirt walks along 5th avenue on Thursday in New York. Kena Betancur / Getty Images Via AFP