|Clearing snow in Montreal|
Freezing rain across much of eastern Canada turned roads and sidewalks into skating rinks and wreaked havoc on holiday plans at one of the busiest travel times of the year.
Snow and ice knocked out power to 400,000 homes and businesses in Michigan, upstate New York and northern New England, and also left more than 400,000 customers without electricity in eastern Canada. It could be days before the lights are back on everywhere.
"Thoughts are with those without power due to the ice storm," Canadian Prime Minister Stephen Harper tweeted. "Please stay safe."
At least nine deaths were blamed on the storm in the US, 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 209kph struck in Arkansas.
Four people were killed in Canada in highway crashes blamed on severe weather conditions. In Toronto, warming centres were set up and the city shut down streetcar service and parts of the subway system. The city's giant Yorkdale Shopping Centre lost power.
Mayor Rob Ford called it one of the worst storms in Toronto's 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," Mr Ford said. "It's not good to wake up and have a freezing cold shower."
Hydro Toronto said about 250,000 customers were without power as ice-coated tree branches snapped and brought down power lines. The utility's vice-president Blair Peberdy said crews were initially focusing on restoring power to two hospitals and a water treatment plant. "We don't want the water systems in Toronto to go down," he said.
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.
In the US, as of midafternoon Sunday, more than 700 airline flights had been canceled and more than 11,000 delayed, according to aviation tracking website FlightAware.com.
In Arkansas, authorities said a woman was killed after a tornado with winds of about 209kph struck in St. Francis County on Saturday. A man found in a field was hospitalised in serious condition, while the woman's 3-year-old granddaughter and 25-year-old daughter were treated at a hospital.
The icy weather was expected to make roads hazardous through tomorrow 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 C from 1998. Records were also set in Wilmington, Delaware, 19.5 C, Atlantic City, New Jersey, 20 C, and Philadelphia 19.5C. Washington tied its 1889 mark at 22C.
Temperatures were expected to return to normal by tomorrow and Wednesday, dropping back into the low single digits.
The scene was much more seasonal in Vermont, where Lynne White of West Charleston listened to the cracking of falling tree branches and gazed at the coating of ice on her home.
"It's actually really pretty," she said. "Not safe, I'm sure, but it's pretty."
Heavy snow in Wisconsin forced dozens of churches to cancel Sunday services. Milwaukee got about 23 centimetres. Ice and snow in Oklahoma were blamed for three traffic deaths on slick roads.
In New York's St. Lawrence County, almost 5cm of ice had accumulated by early Sunday local time, coating tree limbs and power lines, and a state of emergency was declared to keep the roads clear of motorists.
In Canada, crews struggled to restore service where utility companies said power outages affected about 350,000 customers in Ontario, 51,000 in Quebec and 3,000 in New Brunswick.
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 3 million people - about 10% of Canada's population - were 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." photo AP