A severe winter storm that hit some 60% of the United States, alongside Canada, has killed at least 34 people as of Sunday, bringing heavy snow, freezing rain and dangerously low temperatures.

The severe winter storm is nearly unprecedented, with people seeking heat shelters to survive it.

The scope of the storm stretched from the Great Lakes near Canada to the Rio Grande along the border with Mexico. It was expected to claim even more lives as the storm moved east on Sunday.

The storm hit Buffalo in the eastern state of New York hardest on Christmas Day, causing power outages and trapping people inside their cars.

What happened in Buffalo?

The blizzard devastated the city, bringing a total accumulation of snow to nearly 4 feet (1.2 meters) on Sunday.

Erie County Executive Mark Poloncarz said on Twitter that at least 10 people were killed in the county, which also includes Buffalo.

Poloncarz said some of those reported dead were found in cars, while other bodies were recovered in snow banks. He warned that the death toll could increase further.

County-wide driving bans were put in place to contain the situation, with the majority of the area rendered impassable.

"This is not the Christmas any of us hoped for nor expected, but try to have as merry a Christmas as possible today," Poloncarz said on Twitter on Sunday. "My deepest condolences to the families who have lost loved ones."

New York Governor Kathy Hochul addressed the blizzard, saying: "This will go down in history as Buffalo's most devastating storm. This one is for the ages and we're still in the middle of it."

The Reuters news agency cited Hochul as saying that the Biden administration would support the state's request for a federal disaster declaration.

How has the storm affected power?

Power outages persisted well into Christmas Day despite significant restorations. The power-tracking website "PowerOutage.US," reported that as of Sunday evening, less than 100,000 customers were without power across the US.

That figure was down from a peak of 1.7 million customers across the nation who were without electricity at one point due to the storm.

On Sunday evening, over 26,000 residents of New York state remained without power.

In the northeastern state of Maine, 45,800 residents were still without power, the website reported, whereas further south in Virginia, over 9,700 residents were still affected by outages.

Over 1,500 flights were canceled across the US during the Christmas weekend, as of midday on Sunday, crushing the hopes of many US citizens who looked forward to being reunited with family for the first time during Christmas since the start of the coronavirus pandemic.

'Bomb cyclone' to blame for record lows

The National Weather Service called the storm, which started on Thursday, a "once in a generation" event.

Some parts of the country recorded temperatures as low as -55 degrees Fahrenheit (-48 degrees Celsius).

Even in the southern state of Florida, the thermometer dropped below freezing for the first time in almost five years at Tampa International Airport, and hit 43 degrees Fahrenheit (6.1 degrees Celsius) in West Palm Beach.

Forecasters said the extreme cold was powered by a "bomb cyclone," which happens when atmospheric pressure drops very quickly in a strong storm.

The cyclone had developed near the Great Lakes, stirring up blizzard conditions, including heavy winds and snow.