A major ice storm is making its way through southern Ontario.

A significant frontal boundary, from Windsor up to Hamilton and eastwards across Lake Ontario, is expected to remain fairly stationary over the next 12 hours.

Areas south of this front, including Waterloo Region, saw periods of rain Saturday. That rain is expected to turn into freezing rain or ice pellets overnight, followed by flurries on Sunday.

“The models suggest that we could see between 1 to 2 inches of ice in [Waterloo Region],” saysthe University of Waterloo’s Jason Thistlewaite. “We look like we’re in one of the hardest hit areas. Power outages should be expected… especially in the townships.”

Environment Canada says the storm system may bring up to 30 millimetres of rain to the lower Great Lakes. A freezing rain warning remains in effect for those areas as the temperature could fall below zero overnight.

Areas north of the front, from northern Lake Huron to the Ottawa Valley, could also get up to 20 millimetres of freezing rain or drizzle, while others may get snow or ice pellets.

A freezing rain warning remains in effect for the following areas: Waterloo-Wellington, Huron, Perth, Oxford, Brant, Sarnia, Lambton, Elgin, London, Middlesex, Norfolk, Caledonia, Niagara, Kincardine, Belleville, Kingston, Peterborough, and the greater Toronto area.

Environment Canada warns that the storm system’s effects could result in widespread power outages across Ontario due to ice accumulation on trees and power lines.

“The last storm we had in April 2013 of this year wasn’t as severe as this one and we had power outages for about 30,000 across the region,” says Thistlewaite.

Shoppers flocked to stores across the region to stock up ahead of the storm. “I have lots of candles in case the power goes out,” says Beth Robins.

Drivers are being warned about hazardous road conditions as a result of the storm. Motorists and pedestrians “should exercise caution and adjust plans accordingly,” the national weather agency says.

Thistlewaite agrees. “You can’t see freezing rain when it hits the ground. You really shouldn’t be out driving in the weather… it can be incredibly dangerous.”

Deputy Chief Richard Hepditch with the Waterloo Fire Department says its good idea to create a kit with flashlights, an emergency radio, battery-powered lanterns and water. “At least 2 litres of water a day, per person. So that would translate to 6 litres of water minimum over a 72-hour period.”

On Saturday afternoon OPP closed part of the 401 between Prescott and Brockville because vehicles were sliding into the ditch. Two trucks reportedly jackknifed a short distance away.

Holiday travellers are also being urged to check their flight status before heading out to the airport as several travel advisories are in effect.

There have already been cancellations at Toronto’s Pearson International Airport due to poor weather conditions. Some flights at Montreal’s Pierre Elliott Trudeau Airport have also been delayed.

Watch CTV News for your full forecast.

-- With files from The Canadian Press