In Toronto, Canada’s biggest city, more than 250,000 customers of Toronto Hydro were without power as ice-coated tree branches snapped and brought down power lines. As long as 72 hours might be required to restore service, the utility said.

“This is truly one of the worst ice storms we’ve seen here in Ontario,” Toronto Hydro CEO Anthony Haines said on Monday at a press briefing.

Hydro One, another Ontario-based utility, said in a message on Twitter that about 141,000 customers were without power. And about 46,000 Hydro-Quebec customers were without electricity, the Montreal-based company said.

Further east, about 2,900 customers in the province of New Brunswick are without power, New Brunswick Power said.

Not only are winds expected to get stronger, which would bring down more power lines, but ice is building up on some transformers, which could trigger “catastrophic” equipment failures, Haines said.

Toronto’s East General and Sunnybrook hospitals are operating on emergency generators, as is the city’s water-pumping system, Haines said.

“The top priority now is the hospitals,” Toronto Mayor Rob Ford said at a televised press conference, adding that it was too early to declare a state of emergency.

He called it one of the worst storms in recent history. “My house is freezing cold, I have little kids, we might have to go to a hotel tonight. I’m not quite sure what we’re going to do,” Ford said. “It’s not good to wake up and have a freezing cold shower.”

Toronto Hyrdo’s vice-president, Blair Peberdy, said crews were initially focusing on restoring power to two hospitals and a water treatment plant.

Watch: Scenes after the storm

Travellers stranded

More than 300 flights were cancelled at Toronto’s Pearson International Airport, with dozens more scrapped in Ottawa and Montreal.

Air Canada, the country’s biggest airline, said on Monday that it was waiving fees to allow passengers to change flights – space permitting – as the storms impact operations.

Anxious passengers found themselves stranded in airports from Toronto to St. John’s, Newfoundland. Canada’s Via Rail advised commuters to expect delays on its routes between Toronto and Montreal or Ottawa, and police warned people to stay off the roads if possible. One Via Rail train got stuck in Oshawa due to downed power lines.

The sleet also turned some areas into rinks, with residents skating down the streets in Kingston, Ontario, after the storm.

In Toronto, warming centres were set up and the city shut down streetcar service and parts of the subway system – on one of the busiest shopping days of the year. The city’s giant Yorkdale Shopping Centre lost power.

“It’s not just a matter of going in and restoring the power lines,” Toronto Hydro’s Haines said. “Now we’re going to be replacing poles, replacing transformers at the top of some of these poles, so it’s going to be a major event that is going to last days for us to be able to get the power back up.”

So far, the storm’s impact appeared to fall well short of the havoc wreaked by the deadly ice storm that struck eastern Canada in 1998, when more than two dozen people died and about three million people – about 10 per cent of Canada’s population was without power during four days of intermittent freezing rain.

Marie-Eve Giguere, a meteorologist with Environment Canada, said the 1998 storm involved far more freezing rain and ice accumulation than over the past few days.

Freak weather in US

Meanwhile, in the United States, the first full day of winter brought a wild mix of weather on Sunday: ice and high wind in the upper Midwest and northeastern New England states, flooding in the south and record-shattering temperatures in the upper teens and low 20s Celsius along the mid-Atlantic region.

Snow and ice knocked out power to 400,000 homes and businesses in Michigan, upstate New York and northern New England.

At least nine deaths were blamed on the storm, including five people killed in flooding in Kentucky, three traffic deaths on slick roads in Oklahoma and a woman who died after a tornado with winds of 209 km/h struck in Arkansas.

In Kentucky, the bodies of three people were pulled from the Rolling Fork River on Sunday after their vehicle was swept away by floodwaters. A fourth person drowned in Carroll County after a four-wheeler overturned in high water, and a body was discovered in Ballard County near a car abandoned in a flooded ditch.

In Arkansas, authorities said that a woman was killed after a tornado struck in St Francis County on Saturday. A man found in a field was hospitalised in serious condition, while the woman’s three-year-old granddaughter and 25-year-old daughter were treated at a hospital.

Ice and snow in Oklahoma were blamed for three traffic deaths on slick roads.

By mid-afternoon on Sunday, more than 700 flights had been cancelled and more than 11,000 delayed, according to aviation tracking website FlightAware.com.

The icy weather was expected to make roads hazardous until Monday from the upper Midwest to northern New England, just days before Christmas.

At the same time, high-temperature records for the date fell for the second straight day in the mid-Atlantic states because of a mass of hot, muggy air from the South.

In New York’s Central Park, the mercury reached 21 degrees Celsius, easily eclipsing the previous high of 17 degrees Celsius from 1998. Records were also set in Wilmington, Delaware; Atlantic City, New Jersey; and Philadelphia. Temperatures were expected to return to normal by Monday night and Tuesday, dropping back into the low single digits in Celsius.

Further tweets about the ice storm: