Media playback is unsupported on your device Media caption Parts of Niagara Falls freeze

A deadly cold snap that has left the US shivering in record-breaking temperatures for the New Year is expected to worsen in the coming days.

Several deaths have been blamed on the deep freeze, which is forecast to heap more snow on the East Coast this week, the National Weather Service said.

Forty US states were under official winter alerts for bitter cold or snow on Tuesday morning.

Tourists visiting Niagara Falls have posted photos of the waters freezing.

The cold was expected to ease temporarily on Wednesday before the frigid temperatures return on Thursday.

Image copyright Getty Images Image caption New York tourists take a selfie in front of a frozen fountain in Bryant Park

The US National Weather Service tweeted: "Arctic air mass will bring a prolonged period of much-below-normal temperatures and dangerously cold wind chills to the central and eastern US over the next week."

Schools in the eastern and central US have announced closures.

The central US has borne the brunt of the frigid temperatures since the snap began around Christmas.

Omaha, Nebraska, broke a record dating back more than 130 years as teeth chattered in temperatures of -20F (-29C).

Aberdeen, South Dakota, saw the mercury fall to -33F (-36C), breaking a record set in 1919.

Authorities are warning that high winds can drive down temperatures even further, leaving uncovered skin frostbitten in minutes.

Des Moines, Iowa, saw temperatures plummet to -20F (-29C) on Monday, but with the wind chill factored in it felt more like -31F (-35C), officials said.

The normally balmy southern US has not been insulated from the Arctic blast either.

Atlanta, Georgia, recorded a temperature of 13F (-10C) on Tuesday.

Media playback is unsupported on your device Media caption Record cold and hurricane-force winds are ideal conditions for a science experiment

The shores along Mobile Bay, Alabama - in the Gulf of Mexico - saw ocean waters freezing against boat piers.

The wind chill temperature in Tennessee was -6F (-21C).

Only southern Florida and the US South-West have escaped the brutal cold.

Several deaths have been attributed to the cold weather:

In St Louis, Missouri, a homeless man found in a rubbish bin apparently froze to death on Monday evening

Another homeless man, Clyde Chester Parsons, 52, was found dead on a porch in Charleston, West Virginia

Police believe a man found dead outside a church in Detroit, Michigan, froze to death

A 27-year-old woman, Lindsey Klima, found in Fond du Lac County, Wisconsin, on the shores of Lake Winnebago, probably died due to exposure, a sheriff said

In Milwaukee, Wisconsin, two men are thought to have died from hypothermia

A man was found dead near a river in Bismarck, North Dakota

A snowmobiler, Brennan Walpole, 35, died after triggering an avalanche in Lincoln County, Wyoming