A blast of Arctic air is chilling the eastern United States as a polar vortex has started to move southward. Sub-zero temperatures were to grip the region with parts of the Gulf Coast and Florida at risk of freezing conditions.

Heavy snow was hitting the Great Lakes and Appalachian areas, with biting winds making the cold even harsher.

"For some, this could be the heaviest snowfall in over a decade," the National Weather Service (NWS) said. The winter storm has been named Cora.

At least four people have been killed, there have been numerous injuries, thousands of cars have been stuck in ice and snow along roads and almost a quarter of a million homes have lost power, said NPR on Tuesday morning. 

The NWS had also warned that some of the season’s most severe cold will sweep through the south-east. "The coldest air of the season to date and dangerous wind chills are likely across many areas of the south-east," it said.

Temperatures could drop as low as -8°C (18°F) in Texas and -4°C in Georgia, while northern Minnesota could hit a bone-chilling -25°C.

Further south, snow may reach Texas, though accumulations in the south-east are expected to remain modest. However, areas unused to wintry weather could see significant disruption, with the NWS highlighting the risks of icy conditions.

The polar vortex, a mass of icy air circling the Arctic, sometimes shifts, bringing frigid weather to lower latitudes. According to forecasters at Atmospheric and Environmental Research, the vortex will expand over the US in early January, pushing temperatures well below normal for the eastern states.

Winter storms could become more frequent with the climate crisis.

The NWS anticipates more heavy snow later in the month, with widespread snowfall across central and eastern areas. Winds from the Arctic could also bring wind chills of -29°C to -34°C, making frostbite a serious risk.

In 2022, a fierce Arctic storm caused widespread chaos across the US, cutting power to 1.5mn homes and halting oil production at several Gulf Coast facilities. This year, authorities are urging residents to prepare for potentially dangerous conditions.