Alex Pawsey shields herself from the elements with an umbrella while crossing St. George's Square in Guelph, Ont., on Thursday. ((Canadian Press/ Guelph Mercury/ Darren Calabrese))

A snowstorm building in Quebec is expected to hit the Atlantic provinces later Friday, after pounding southern Ontario and causing a slew of traffic accidents there.

The storm is forecast to dump up to 25 centimetres of snow on Montreal and 30 centimetres on Quebec City before reaching the Maritime provinces in time for supper.

Friday wasa snow day for most students in the greater Montreal region, as all major school boards called off classes for the day.

Many flights were cancelled at Trudeau Airport.

While theEastern Townships are forecast to see less snowfall, they will likely be hit with ice pellets and freezing rain.

Meanwhile, across Ontario,thousands of residents woke up Friday morning in homes without power.

Hydro One spokesman Daffyd Roderick told CBC Newsworld the utility was aware of roughly 80,000 households and businesses that had no electricity, and that the number is expected to climb.

Hydro crews were alerted to 25 snapped poles on Thursday afternoon, but the main obstacle facing power crews is how to get there, he said.

"There's only so much we can do until Mother Nature does her work, and then we can set about repairing ... when conditions are safe out there."

The power failures have affected portions of southwestern Ontario from Strathroy and Walkerton to Newmarket and the GTA.

"Very few parts are unscathed today," Roderick said, adding the hardest-hit areas may need to wait between three and five days to see the situation restored to normal.

Storm blamed in deaths of 2 children

Ontario roads are flooded or slick with ice, and more freezing rain and snow on Friday could make driving conditions just as treacherous as the previous day, when the intense winter storm was blamed in the deaths of two children.

Police said the children — seven-year-old Anita Hiebert and her six-year-old brother Pancho — died Thursday when a car and a truck collided on an icy, snow-blown road near the town of Listowel northwest of Kitchener. The children's mother, Christina Hiebert, is in critical condition in a London hospital.

Police and tow trucks responded to hundreds of other crashes across southern Ontario, as blowing snow and ice pellets created slippery conditions and poor visibility.

The storm caused headaches for rush-hour commuters on highways. Complicating the issue was a CN freight train derailment east of Toronto in the morning that caused disruptions for eastbound commuter and Via Rail trains.

The storm, which started in the U.S. Midwest, was tracking east, with heavy snow expected in Ottawa overnight, Montreal by Friday morning and Halifax by Friday afternoon.

Flight delays

About 100 flights were cancelled or delayed Thursday at Pearson International Airport in Toronto. Officials at Pearson said travellers could expect more cancellations and delays Friday.

The storm is part of an intensifying system tracking northeastward from the U.S., after tapping warm moist air from the Gulf of Mexico.

The same storm system caused tornadoes to touch down in two U.S. states, killing at least eight people in Alabama and a seven-year-old child in Missouri.