Polar cold persisted on Monday across a large part of the United States where a major winter storm caused the death of at least eleven people, also leaving more than a million homes without electricity and grounding thousands of planes.

Authorities have warned that a mass of Arctic air will cause temperatures to plummet to dangerously low levels for several more days.

A state of emergency has been declared in about twenty states as well as in the federal capital, Washington.

Considered by some meteorologists to be one of the worst winter episodes in recent decades in the United States, the storm is accompanied by freezing temperatures, heavy snowfall and ice accumulations with potentially "catastrophic" consequences, according to the National Weather Service (NWS).

New York City Mayor Zohran Mamdani said five people were found dead outdoors over the weekend in freezing temperatures.

"While we do not yet know the causes of their deaths, nothing serves as a stronger reminder of the danger of extreme cold and the vulnerability of many residents, especially homeless New Yorkers," he said at a press conference Sunday.

In Texas, authorities confirmed three deaths, including that of a 16-year-old girl killed in a sledding accident. Two people died of hypothermia in Louisiana.

In addition, one person was killed and two others injured Saturday in a collision related to winter conditions in southeastern Iowa, according to local state police.

Some 820,000 customers were still without power Monday morning, mainly in the Southern United States, according to the specialized website PowerOutage.com.

In Tennessee, where ice brought down power lines, more than 250,000 customers remained without power on Monday, while 100,000 customers were without power in Louisiana and Mississippi.

Authorities from Texas to North Carolina and New York urged residents to stay home due to the perilous conditions.

"Avoid taking to the road unless absolutely necessary," the Texas Division of Emergency Management posted on X.

Polar Vortex

The storm was moving northeast on Sunday, dumping snow on major densely populated cities including Philadelphia, New York and Boston.

"We will continue to monitor and stay in touch with all states that are in the path of this storm. Stay safe and stay warm!", urged US President Donald Trump on his Truth Social platform.

Several major airports in the capital Washington, Philadelphia and New York were virtually at a standstill, as more than 19,000 flights to and from the United States have been canceled since Saturday and thousands more have been delayed, according to the FlightAware website.

The FAA, the US aviation regulatory authority, indicated on its X account that a small plane carrying eight people crashed Sunday evening during takeoff at an airport in Maine (northeast) without specifying whether weather conditions were related to the accident.

The storm is linked to a deformation of the polar vortex, a mass of air that usually circulates above the North Pole, but which has stretched southward.

Scientists believe that the increasing frequency of these vortex disturbances could be linked to climate change, although the debate is not settled and natural variability also plays a role.

An avowed climate skeptic, Donald Trump nevertheless used the storm as a pretext to express his skepticism again on his Truth Social platform: "Could the environmental insurgents please explain to me: WHAT HAPPENED TO CLIMATE CHANGE?".

Authorities have warned of potentially deadly cold that could last for a week after the storm, particularly in the Northern Great Plains and other central regions, where wind chill could reach -45°C.

Such temperatures can cause frostbite in minutes.