A strong winter storm that slammed the South with snow showers and ice over the weekend moved north on Monday, dropping heavy snow over parts of the Northeast and Canada, where gusty winds made travel treacherous.

While New York City and other points along the East Coast mostly experienced a mix of rain and high winds, some of the hardest-hit places over the long holiday weekend were among the least prepared.

Thousands of people in the Southeast were still without electricity on Monday night, with warnings that the power might take days to return in some places. Hundreds of flights were canceled. Numerous car accidents were reported on icy roads, including one that killed two people in Raleigh, N.C.

Digging out down South, if you have a shovel.

Tiffany Graves, 46, of Charlotte, N.C., said that, as a Southerner, she had felt unprepared during snowstorms in years past.

But on Sunday morning, as the sleet hit her window, she said she “sort of went into panic mode” and prepared for the worst: cold tuna sandwiches on standby in case the power went out; battery packs charged; ice scraper ready.

Still, on Monday, as she saw neighbors shoveling snow from cars and streets outside, she realized a gap in her planning: She had no shovel of her own. But she did have electricity, unlike many in her state who were still waiting.

The snow was more of an overnight wonder in Canton, Miss., where up to nine inches of snow dropped on Sunday. On Monday afternoon, residents were mostly relaxing as the snow melted away from porches and parks, the captain of the Fire Department said.

“People were just excited about the snow, and it all melted by that evening,” Capt. Eric Redmond said. “It’s not normal for us to get that much snow down here.”

Winter storm warnings reach north to Canada.

Winter storm warnings stretched from western North Carolina up through Maine, according to the National Weather Service.

The storm played out in typical fashion near Lake Erie. Ashtabula, Ohio, which is northeast of Cleveland and next to the lake, had received 27 inches, the National Weather Service said. Freezing rain and sleet turned into snow in western Pennsylvania.

Buffalo lived up to its reputation, with totals of up to 16 inches and gusty winds reaching as high as 40 miles per hour through the day.

Across the border, the city of Toronto issued a winter storm warning Monday afternoon, hours after snow had risen past the knees of morning dog-walkers in some parts of the city, the fourth-largest in North America, on the shore of Lake Ontario. The city ended the warning just after 5 p.m.

The police closed two of Toronto’s main intercity highways. The schools, which had been finally slated to open for in-person learning for the first time since Christmas break, were closed, with students returning to another day of online instruction in many cases.

One of Canada’s most powerful politicians, Doug Ford, the Ontario premier, spent part of the day using his truck to personally yank out cars stuck in snow banks, and drive stranded drivers home.

A video of him joining a crew to dig out a car circulated on social media, inspiring critical responses from wary citizens who have suffered some of the most strict Covid regulations of North America.

“It’s an absolute mess right now,” Mr. Ford told a local news reporter.

Where the snow turned to rain, flooding was a risk. Most of the New York City area, including parts of New Jersey, was under a coastal flood warning or advisory that ended by 4 p.m., the Weather Service said.

Up to four inches of snow fell in central New Jersey, and parts of the Lower Hudson Valley had accumulated about six inches of snow.

The Weather Service said there were gusts of over 60 miles per hour along the Connecticut and New York coasts, but added that the strongest winds had passed by Monday afternoon. Driving remained difficult to impossible in some regions of the Northeast, particularly in areas forecast to receive high winds, which could bring down tree branches.

Anne Strauser, a National Weather Service meteorologist in Maine, said the center of the storm was just north of the state and would continue moving northeast into the Canadian maritime provinces and into the Atlantic Ocean.

As the storm moves, people in the northern part of Maine can expect a sharp drop in temperatures — “as low as mid-teens below zero,” she said. “The air that is moving in behind the storm is moving in from northern Canada, where it is much colder,” Ms. Strauser said.

And according to the Weather Service office in Wakefield, Va., there is a potential for snow or a “wintry mix” in the coming days for the central parts of the state, as well as southeast Maryland and northeast North Carolina.

.

The storm has disrupted travel and left thousands without power.

By 10 p.m. Monday, more than 1,700 flights within, into or out of the United States had been canceled, according to FlightAware, with more than 400 cancellations for flights in and out of Charlotte Douglas International Airport alone.

Amtrak canceled more than a dozen trains on Monday, including service between Washington and Chicago and service between Harrisburg, Pa., and New York.

Highway travel on icy roads in the South proved especially treacherous. Two people were killed in a car accident on Sunday east of Raleigh, N.C., after driving off the road into trees, The Associated Press reported.

In Virginia, there were more than 400 crashes but no deaths, the State Police said.

The storm also left tens of thousands of customers without electricity from Georgia to Massachusetts, according to PowerOutage.us, which aggregates data from utilities across the United States.

By Monday evening, about 5,000 customers in Georgia remained without power, and in North Carolina, there were more than 8,000 customers still waiting for electricity to come back on, the tracking site said.

Gov. Henry McMaster of South Carolina had warned on Saturday that some people could remain without power for “three or four days.”

In the South, where some governors declared states of emergency, areas such as central Mississippi and central North Carolina had received more than nine inches of snow, while parts of central South Carolina and the mountainous regions of North Carolina had up to half an inch of ice, the National Weather Service said.

Gov. Roy Cooper of North Carolina had warned residents at a news conference on Sunday to stay off the roads because parts of the state had received up to a foot of snow. On Monday, some roads in the central part of the state remained slick with ice, said Marty Homan, a spokesman for the Department of Transportation.

The storm system also spawned two tornadoes in southwestern Florida on Sunday morning, the Weather Service said. There were no reports of deaths, local officials said.

Three people were treated for minor injuries, and there was widespread damage, including to 108 mobile homes in three parks in the Iona McGregor section of Fort Myers, Fla., said Richard Rude, a meteorologist with the National Weather Service in Tampa. About 200 people were displaced, local officials said.

Grace Ashford, Jesus Jiménez, Jenny Gross and Christine Chung contributed reporting.