Tens of millions of Americans endured bone-chilling temperatures, blizzard conditions, power outages and canceled holiday gatherings Friday from a winter storm that forecasters said was nearly unprecedented in its scope, exposing about 60% of the U.S. population to some sort of winter weather advisory or warning.

More than 200 million people were under an advisory or warning on Friday, the National Weather Service said. The weather service’s map “depicts one of the greatest extents of winter weather warnings and advisories ever,” forecasters said.

More than 3,400 flights within, into or out of the U.S. were canceled Friday, according to the tracking site FlightAware, causing more mayhem as travelers try to make it home for the holidays. Some airports, including Seattle-Tacoma International Airport, closed runways.

More than 458,000 homes and businesses were without power Friday morning.

The huge storm stretched from border to border. In Canada, WestJet canceled all flights Friday at Toronto Pearson International Airport, beginning at 9 a.m. And in Mexico, migrants waited near the U.S. border in unusually cold temperatures as they awaited a U.S. Supreme Court decision on whether and when to lift pandemic-era restrictions that prevent many from seeking asylum.

This satellite image made available by NOAA shows weather systems across North America on Dec. 23, 2022, at 10:56 a.m. EST.

This satellite image made available by NOAA shows weather systems across North America on Dec. 23, 2022, at 10:56 a.m. EST.

“This is not like a snow day when you were a kid,” President Joe Biden warned Thursday after a briefing from federal officials. “This is serious stuff.”

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.

Among those with canceled flights was Ashley Sherrod, who planned to fly from Nashville, Tennessee, to Flint, Michigan, on Thursday afternoon.

“My family is calling, they want me home for Christmas, but they want me to be safe, too,” said Sherrod, whose bag — including the Grinch pajamas she was planning to wear to a family party — was packed and ready by the door.

Activists also were rushing to get the homeless out of the cold. In Chicago, Andy Robledo planned to spend the day organizing efforts to check on unhoused people who have received tents, propane heaters and other supplies through his nonprofit, Feeding People Through Plants.

Robledo and volunteers build the tents modeled on ice-fishing tents, including a plywood subfloor, and offer them to people living on the streets in Chicago.

“It’s not a house, it’s not an apartment, it’s not a hotel room. But it’s a huge step up from what they had before,” Robledo said.

In Portland, Oregon, officials opened four emergency shelters. It was so cold in the city that Taylor Bailey lost all sensation in her hands as she cycled to her job at at iconic bike rental, repair and touring store Cycle Portland in the frigid temperatures.

“It’s the wind, really, that’s so cold. The wind is absolutely bitter,” she said Thursday, adding that even her gloves didn’t help.

The weather service is predicting the coldest Christmas in more than two decades in Philadelphia, where school officials shifted classes online Friday. Some surrounding districts canceled classes altogether.

In South Dakota, Gov. Kristi Noem late Thursday activated the state’s National Guard to haul firewood from the Black Hills Forest Service to the Rosebud Sioux Tribe as some members were stranded in their homes with dwindling fuel.

Scot Eisenbraun, who runs a farm and ranch near Wall in western South Dakota, said he’s lost several cattle in recent days. The cold is life-threatening if you are caught outside, he said, so people travel in groups of two vehicles in case one gets stranded.

“Dress really warm and don’t get stuck outside really long,” he said.

Most of western and parts of northern Michigan were under blizzard warnings, according to the weather service. On the other side of the state, the zoo and an art museum in Detroit were closing. And to the north of the city, a rescue team used a Hovercraft to reach an injured swan Thursday that became frozen to ice on a lake.

Buffalo, New York, Mayor Byron Brown urged people to stay home as meteorologists warned that the city could see 2 to 4 feet (0.6 to 1.2 meters) of snow through the weekend.

While New England was being spared the numbing cold and snow, heavy rain and wind gusting to more than 60 mph (96 kph) knocked out power to thousands. About 150,000 homes and businesses in Massachusetts, Rhode Island, Maine, New Hampshire and Vermont had no electricity as of Friday morning, according to the region’s major utilities. There were another 100,000 outages in Connecticut.

Hundreds of utility and tree crews were deployed, but the high winds hampered them. The limit for using bucket trucks is typically 25 mph (40 kph) to 35 mph (56 kph), a utility official said.

In Maine, gusts approaching 70 mph (113 kph) were reported along the coast Friday morning. Atop New Hampshire’s Mount Washington, the tallest peak in the Northeast, the wind topped 130 mph (210 kph).

It was so bad in Vermont that Amtrak canceled service for the day, and nonessential state offices were closing early.

“I’m hearing from crews who are seeing grown trees ripped out by the roots,” Mari McClure, president of Green Mountain Power, the state’s largest utility, said at a news conference.