Hundreds of thousands of households in the US have no power as a major storm rolls across the country, which is also leading to flight cancellations and road closures.

Snow, ice and freezing rain are creating “life threatening” conditions stretching from Texas to New England that could last for several days, according to the National Weather Service (NWS).

At least two people died of hypothermia in Louisiana, with state health officials linking their deaths to the storm, and another death was reported in Texas.

As of Sunday afternoon, more than 1 million households had lost power, according to poweroutage.us. Meanwhile, more than 10,000 flights were cancelled, FlightAware reported.

Around 180 million Americans – more than half the population – are set to be affected by widespread heavy snow, sleet and freezing rain, which is a dangerous phenomenon where cooled rain droplets freeze instantly on surfaces.

“The snow and the ice will be very, very slow to melt and won’t be going away anytime soon, and that’s going to hinder any recovery efforts,” Allison Santorelli, a meteorologist with the National Weather Service, told the BBC’s US media partner CBS News.

Kentucky Governor Andy Beshear said in a news conference on Sunday that the state was seeing more ice and less snow than was originally predicted.

“That is not good news for Kentucky,” he said. “What it means is that the roads are that much more dangerous and that the dangerous conditions are going to extend into next week.”

Weather experts have warned that one of the biggest dangers of the storm is ice, which has the potential to damage trees, down power lines and make roads unsafe.

More than 200 car crashes were reported in the state of Virginia as the storm moved into the state, according to local media.

Louisiana’s Department of Health confirmed on Sunday that the two men who died of hypothermia were in Caddo Parish, a region which contains the city of Shreveport.

The mayor of Austin, Texas, Kirk Watson, posted on social media on Sunday that “we have experienced the first fatality related to this winter storm. This fatality is exposure-related”.

New York City Mayor Zohran Mamdani wrote in a post on X that at least five people in the city had died on Saturday but added their cause of death was yet to be determined. He said, however, “it is a reminder that every year New Yorkers succumb to the cold”.

Nearly half the states have declared emergencies, and schools across the country are already canceling classes in anticipation of the storm continuing into Monday. The US Senate has also scrapped a scheduled vote for Monday evening.

In declaring an emergency in the nation’s capital, Washington Mayor Muriel Bowser said: “We’re experiencing the biggest snowstorm in a decade in DC this weekend.”

While places in the north such as the Dakotas and Minnesota are used to below- freezing temperatures in winter, it is unusual to see such extreme cold in states like Texas, Louisiana and Tennessee, where temperatures are around 15-20C below the seasonal average.

Those states could also see ice accretions of around an inch caused by freezing rain, a dangerous phenomenon where supercooled rain droplets freeze instantly on surfaces.

Mayor Watson and other officials in those areas are warning residents that ice and snow can melt during the day and then refreeze once the sun sets, also creating dangerous conditions on roads and weighing down power lines.

The Nashville Electric Service says more than 200,000 of Tennessee’s outages are in and around the Nashville area. And that residents can expect to be without power for several days.

“We’re really worried about ice accumulation and what that might do to roadway safety and to our power infrastructure,” said Tennessee Emergency Management Director Patrick Sheehan said in a video statement.

The polar vortex – a ring of strong westerly winds that form above the Arctic every winter containing a pool of very cold air – led to the powerful storm, according to weather experts.

When the winds are strong, they stay in place, however when the winds weaken, the vortex loops further south and cold air plunges toward the US. As the cold air meets mild air in the south, the air rises and storm fronts form.

In this case, the winter storm is pushing northwards and eastwards, clearing the Canadian maritime by Tuesday but leaving more cold air in its wake. It is forecast to stay dangerously cold into the start of February.

Some experts contend climate change could influence the behaviour of the polar vortex due to changes in sea surfaces temperatures in our warming world.