U.S. emergency crews counted the grim costs of a colossal winter storm that brought Christmas chaos to millions, especially in hard-hit western New York, where the death toll reached 25 on Monday in what authorities described as a "war with Mother Nature."

Blizzard conditions continue to prevail in parts of the U.S. Northeast. The stubborn remnants of a massive sprawl of extreme weather, including severe cold that gripped the country over several days, has caused widespread power outages, travel delays and at least 47 deaths nationwide.

"Much of the eastern United States will remain in a deep freeze through Monday before a moderating trend sets in on Tuesday," said the NWS in its latest advisory.

The extreme weather forced the cancellation of more than 15,000 flights in recent days including more than 1,700 on Monday, according to tracking site Flightaware.com.

Buffalo – a U.S. city that is no stranger to foul winter weather – has been buried under staggering amounts of snow, with the National Weather Service forecasting up to 14 inches (0.35 meters) for Monday in addition to the several feet that have already left the city marooned coupled with a virtual collapse of emergency services.

The blizzard has stubbornly refused to release its grip on western New York's Erie County, where Buffalo is located and which has become the epicenter of the crisis.

"It is (like) going to a war zone, and the vehicles along the sides of the roads are shocking," said New York Governor Kathy Hochul, a Buffalo native, where 2.4-meter (8-foot) snow drifts and power outages created life-threatening conditions.

Hochul told reporters on Sunday evening that residents were still in the throes of a "very dangerous life-threatening situation" and warned everyone in the area to remain indoors. The Governor said she was stunned by what she saw during a Sunday reconnaissance tour of the city. "It is (like) going to a war zone, and the vehicles along the sides of the roads are shocking," Hochul said, describing snow drifts against homes and how power outages made for life-threatening conditions. "This is a war with Mother Nature," she said. The extreme weather sent wind chill temperatures in all 48 contiguous U.S. states below freezing over the weekend.

Worst in 45 years

There have been 32 confirmed weather-related deaths across nine states, including at least 13 in Erie County where Buffalo is located, with officials warning the number is expected to rise.

Officials described historically dangerous conditions in the snow-prone Buffalo region, with hours-long whiteouts and bodies discovered in vehicles and under snow banks as emergency workers struggled to search for those in need of rescue.

The city's international airport remains closed until Tuesday and a driving ban remained in effect for all of Erie County.

"We now have what will be talked about not just today but for generations (as) the blizzard of 2022," Hochul said, adding that the severity had surpassed the region's prior landmark snowstorm of 1977 in "intensity, longevity, wind ferocity."

Due to frozen electric substations, some residents were not expected to access power until Tuesday, with one substation reportedly buried under 18 feet of snow, informed a senior county official.

'Conditions are just so bad'

The NWS earlier warned that blizzard conditions in western New York's Great Lakes region had continued into Sunday, with "additional snow accumulations of 2 to 3-feet through (Sunday night)."

A couple in Buffalo, across the border from Canada, told AFP on Saturday that with the roads completely impassible, they would not be making a 10-minute drive to see their family for Christmas. "It's tough because the conditions are just so bad. A lot of fire departments are not even sending out trucks for calls," said 40-year-old Rebecca Bortolin.

The storm forced the cancellation of nearly 3,000 U.S. flights on Sunday, in addition to some 3,500 scrapped on Saturday and nearly 6,000 on Friday, according to the tracking website Flightaware.com.

More than 1,000 U.S. flights had already been canceled just hours into Monday, the website reported.

Travelers remained stranded or delayed at airports throughout Christmas Day including at major hubs in Atlanta, Chicago, Denver, Detroit and New York.

The icing on roads and white-out conditions also led to temporary closures of some of the nation's busiest transport routes, including the cross-country Interstate 70.

Drivers were being warned not to take to the roads – even as the nation reached what is usually its busiest annual travel time.

The extreme weather has severely taxed electricity grids, with multiple power providers urging millions of people to reduce usage to minimize rolling blackouts in places like North Carolina and Tennessee.

At one point on Saturday, nearly 1.7 million customers were without electricity in the biting cold, according to the tracker, poweroutage.us.

The figure dropped substantially by Sunday night, although more than 50,000 customers in eastern states still lacked power.

The fierce winter conditions are also taking a toll in Canada. A weekend bus mishap in British Columbia, that was believed to have been caused by icy roads, left four people dead and sent 53 to the hospital, including two still in critical condition early on Sunday.

Hundreds of thousands were left without power in Ontario and Quebec. Many flights were canceled in major cities and passenger train services between Toronto and Ottawa were suspended.