A major winter storm that pounded several U.S. states over the holidays made its way across the border Wednesday, bringing heavy snow and dangerous road conditions to southern Ontario.

Environment Canada and police agencies warned drivers to be vigilant and avoid travel if possible as the snow system arrived from Kentucky. The storm was expected to cross over Ontario overnight Wednesday and then hit parts of Quebec.

In some areas, blowing snow and icy roads caused multiple vehicle accidents, forcing Ontario Provincial Police to temporarily shut down some major expressways, including a stretch of Highway 401 near London and a section of Highway 403 near Hamilton.

Boxing Day shoppers and travellers had to contend with snowfall and high winds that were expected to continue into Thursday morning, when the snow will lighten to flurries.

A special weather statement issued by Environment Canada said the highest snowfall amounts were expected over Dunnville, Niagara and a swath of Ontario stretching from Kingston to Cornwall. Winter storm warnings are in effect for all three areas.

Between 15 and 20 centimetres of snowfall combined with northeast wind gusts of up to 70 km/h are expected for the Niagara area. The combined heavy snow fall and gusting winds will result in reduced visibility, often less than 500 metres.

In eastern Ontario, 15 centimetres of snow were expected to fall by Thursday afternoon. Reduced visibility is also predicted for the region.

The Greater Toronto Area was expecting to see the least amount of snowfall, with the national weather agency forecasting five to 10 centimetres of snow beginning Wednesday afternoon to be accompanied by wind gusts hitting 50 km/h.

Peter Noehammer, director of Toronto’s transportation services, told CP24 that the city’s salt trucks and plows are poised for action.

Noehammer said the city’s plows will clear the expressways when 2 cm have fallen. The main roads will be plowed when 5 cm have fallen and the side streets will be plowed when 8 cm have fallen.

Snow removal crews are ready to work through Thursday to clear the city’s streets, he said.

Meanwhile, Environment Canada has also issued a winter storm warning for the Montreal-Laval area and surrounding parts of southern Quebec.

The area is predicted to be hit with 15 to 25 cm of snow, beginning early Thursday morning. Blowing snow gusts are also expected, which will reduce visibility, warns Environment Canada.

Storm’s deadly path in the U.S.

Six deaths are being blamed on hazardous winter storms that swept across the U.S. south and its midsection on Christmas Day and Boxing Day.

According to FlightAware.com, over 325 flights around the U.S. were cancelled as of Wednesday morning.

Pearson International Airport delayed or cancelled over 100 incoming and outgoing flights to Canada and the U.S.

Fast-moving storms south of the border wreaked havoc on holiday travel plans with blizzard conditions in the mid-U.S and a string of tornadoes in the south.

An estimated 71,000 homes in Arkansas were without power on Christmas Day as freezing rain damaged utility lines throughout the state. Blizzard conditions were also forecasted for parts of Illinois, Indiana and western Kentucky with predictions of 10 to 18 centimetres of snow.

Across southern U.S. states, a number of tornados knocked down trees, blew the roofs off homes and left thousands celebrating Christmas in the dark.

A tornado warning remains in effect in Alabama where the storms were blamed for three deaths. In Louisiana a number of homes were damaged and individuals were injured following a tornado that touched down on the state.

Mississippi Gov. Phil Bryant declared a state of emergency after a tornado sent eight people to hospital and caused damage in eight counties while at least three tornadoes hit Texas.

With files from The Associated Press and The Canadian Press