Millions of people hunkered down against a deep freeze Sunday to ride out the winter storm that has killed at least 29 people across the United States and is expected to claim more lives after trapping some residents inside houses with heaping snow drifts and knocking out power to several hundred thousand homes and businesses.

The scope of the storm has been nearly unprecedented, stretching from the Great Lakes near Canada to the Rio Grande along the border with Mexico. About 60 per cent of the US population faced some sort of winter weather advisory or warning, and temperatures plummeted drastically below normal from east of the Rocky Mountains to the Appalachians, the National Weather Service said.

Travellers’ weather woes are likely to continue, with hundreds of flight cancellations already and more expected after a bomb cyclone — when atmospheric pressure drops very quickly in a strong storm — developed near the Great Lakes, stirring up blizzard conditions, including heavy winds and snow. Some 1707 domestic and international flights were cancelled on Sunday as of about 2pm EDT, according to the tracking site FlightAware.

The storm unleashed its full fury on Buffalo, with hurricane-force winds and snow causing whiteout conditions, and paralysing emergency response efforts. New York Gov. Kathy Hochul said almost every fire truck in the city was stranded Saturday. Officials said the airport would be shut through Tuesday morning. The National Weather Service said the snow total at the Buffalo Niagara International Airport stood at 109 centimetres at 7am Sunday (US time).

Daylight revealed cars nearly covered by 1.8m snowdrifts and thousands of houses, some adorned in unlit holiday displays, dark from a lack of power. With snow swirling down untouched and impassable streets, forecasters warned that an additional 1 to 2 feet of snow was possible in some areas through early Monday morning amid wind gusts of 65km/h.

Two people died in their suburban Cheektowaga, New York, homes Friday when emergency crews could not reach them in time to treat their medical conditions, and another died in Buffalo. Four more deaths were confirmed overnight, bringing the total to seven in Erie County. County executive Mark Poloncarz warned there may be more dead.

“Some were found in cars, some were found on the street in snowbanks,” said Poloncarz. “We know there are people who have been stuck in cars for more than two days.”

Freezing conditions and day-old power outages had Buffalonians scrambling to get to anywhere that had heat amid what Hochul called the longest sustained blizzard conditions ever in the city. But with streets under a thick blanket of white, that wasn’t an option for people like Jeremy Manahan, who charged his phone in his parked car after almost 29 hours without electricity.

“There’s one warming shelter, but that would be too far for me to get to. I can’t drive, obviously, because I’m stuck,” Manahan said. “And you can’t be outside for more than 10 minutes without getting frostbit.”

Ditjak Ilunga of Gaithersburg, Maryland, was on his way to visit relatives in Hamilton, Ontario, for Christmas with his daughters Friday when their SUV was trapped in Buffalo. Unable to get help, they spent hours with the engine running, buffeted by wind and nearly buried in snow.

By 4am Saturday, their fuel nearly gone, Ilunga made a desperate choice to risk the howling storm to reach a nearby shelter. He carried 6-year-old Destiny on his back while 16-year-old Cindy clutched their Pomeranian puppy, following his footprints through drifts.

“If I stay in this car I’m going to die here with my kids,” Ilunga recalled thinking. He cried when the family walked through the shelter doors. “It’s something I will never forget in my life.”

The storm knocked out power in communities from Maine to Seattle. But heat and lights were steadily being restored across the US. According to poweroutage.us, less than 300,000 customers were without power at 8am EDT Sunday - down from a peak of 1.7 million. In North Carolina, less than 6600 customers had no power - down from a peak of 485,000 or more.

Gamaliel Vega tries to dig out his car on Lafayette Avenue after he got stuck in a snowdrift about a block from home while trying to help rescue his cousin, who had lost power and heat with a baby at home across town during a blizzard in Buffalo, N.Y. Photo / AP

Concerns about rolling blackouts across eastern states subsided Sunday after PJM Interconnection said its utilities could meet the day’s peak electricity demand. The mid-Atlantic grid operator had called for its 65 million consumers to conserve energy amid the freeze Saturday.

Across New England, power has been restored to tens of thousands with just under 90,000 people, mostly in Maine, still without electricity. In New York, more than 39,000 households were still without power Sunday, including 27,000 in Erie County, where utility crews and hundreds of National Guard troops battled high winds and struggled with getting stuck in the snow.

Storm-related deaths were reported in recent days all over the country: seven in Erie County, New York; 10 in Ohio, including an electrocuted utility worker and those killed in multiple car crashes; four motorists killed in crashes in Missouri and Kansas; a Vermont woman struck by a falling branch; an apparently homeless man found amid Colorado’s subzero temperatures; a woman who fell through Wisconsin river ice.

In Jackson, Mississippi, city officials on Christmas Day announced that residents must now boil their drinking water due to water lines bursting in the frigid temperatures.

In Florida, the thermometer plunged below freezing for the first time in almost five years at Tampa International Airport, and hit 43 degrees (6.1 degrees Celsius) in West Palm Beach, according to the National Weather Service. The temperature drop and freezing sleet were conducive to cold-blooded iguanas falling out of trees.

Along Interstate 71 in Kentucky, Terry Henderson and her husband, Rick, weathered a 34-hour traffic jam in a rig outfitted with a diesel heater, a toilet and a refrigerator after getting stuck trying to drive from Alabama to their Ohio home for Christmas.

“We should have stayed,” Terry Henderson said after they got moving again Saturday.

In Buffalo, William Kless was up at 3 am Sunday. He called his three children at their mother’s house to wish them Merry Christmas and then headed off on his snowmobile for a second day spent shuttling people from stuck cars and frigid homes to a church operating as a warming shelter.

Through heavy, wind-driven snow, he brought about 15 people to the church in Buffalo on Saturday, he said, including a family of five transported one by one. He also got a man in need of dialysis, who had spent 17 hours stranded in his car, back home, where he could receive treatment.

“I just felt like I had to,” Kless said.