BUFFALO, N.Y. >> Millions of people hunkered down in a deep freeze overnight and early morning to ride out the frigid storm that has killed at least 18 people across the United States, trapping some residents inside homes with heaping snow drifts and knocking out power to hundreds of thousands of 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% of the U.S. 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.

More than 2,360 domestic and international flights were canceled Saturday, according to the tracking site FlightAware.

Forecasters said a bomb cyclone — when atmospheric pressure drops very quickly in a strong storm — had developed near the Great Lakes, stirring up blizzard conditions, including heavy winds and snow.

The storm unleashed its full fury on Buffalo, with hurricane-force winds and snow causing whiteout conditions, paralyzing emergency response efforts — New York Gov. Kathy Hochul said almost every fire truck in the city was stranded — and shutting down the airport through Monday, according to officials.

Freezing conditions and day-old power outages had Buffalonians scrambling Saturday to get out of their homes to anywhere that had heat. But with city 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.”

Mark Poloncarz, executive of Erie County, home to Buffalo, said ambulances were taking more than three hours to make a single hospital trip and the blizzard may be “the worst storm in our community’s history.”

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, he said, and another died in Buffalo.

“We can’t just pick up everybody and take you to a warming center. We don’t have the capability of doing that,” Poloncarz said. “Many, many neighborhoods, especially in the city of Buffalo, are still impassable.”

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 in the vehicle buffeted by wind and nearly buried in snow.

By 4 a.m. Saturday, with 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, stepping into his footprints as they trudged through drifts.

“If I stay in this car I’m going to die here with my kids,” he recalled thinking, but believing they had to try. 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, and a major electricity grid operator warned 65 million people across the eastern U.S. of possible rolling blackouts.

Across the six New England states, more than 273,000 customers remained without power on Saturday, with Maine the hardest hit. Some utilities said electricity may not be restored for days.

In North Carolina, 169,000 customers were without power Saturday afternoon, down from more than 485,000. Utility officials said rolling blackouts would continue for the next few days.

Storm-related deaths were reported in recent days all over the country: Four dead in an Ohio Turnpike pileup involving some 50 vehicles; four motorists killed in separate crashes in Missouri and Kansas; an Ohio utility worker electrocuted; 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 Mexico, migrants camped near the U.S. border were facing unusually cold temperatures as they awaited a U.S. Supreme Court decision on pandemic-era restrictions preventing many from seeking asylum.

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.

Poloncarz of Erie County tweeted late Saturday that 34.6 inches (about 88 centimeters) of snow had accumulated at the Buffalo Airport and drifts were well over 6 feet (1.8 meters) in some areas. Blizzard conditions were expected to ease early Sunday, he continued, but continuing lake effect snow was forecast.

Vivian Robinson of Spirit of Truth Urban Ministry in Buffalo said she and her husband have been sheltering and cooking for 60 to 70 people, including stranded travelers and locals without power or heat, who were spending Saturday night at the church.

Many arrived with ice and snow plastered to their clothes, crying, their skin reddened by the single-digit temperatures. On Saturday night, they prepared to spend Christmas together.

“It’s emotional just to see the hurt that they thought they were not going to make it, and to see that we had opened up the church, and it gave them a sense of relief,” Robinson said. “Those who are here are really enjoying themselves. It’s going to be a different Christmas for everyone.”