Ontario was waking up to a worst snow storm in four years after forecasters issued warning earlier of a very treacherous traffic conditions Friday morning.

Environment Canada issued a warning Thursday that the snow storm that arrived in the evening would mark its way through Toronto, southern Ontario, leaving as much as 25 centimeters of snow on its path.

The snow storm is said to have formed when a low pressure system arrived in southern Ontario from Michigan and Lake Huron Thursday afternoon and grew stronger by evening.

"It might be the biggest storm since 2011," the Star quoted severe weather meteorologist Rob Khun, of Environment Canada as saying.

"Friday morning rush hour has a good potential to be a mess. Snow could be heavy, with low visibility, and some blowing and drifting," Khun was quoted as saying by the newspaper.

The snowstorm has also affected travelers planning to fly as 8 percent of flights out of Pearson and 3 percent out of Billy Bishop had been cancelled, the Star reported.

"Toronto Pearson has invested in infrastructure, equipment and staff training for effective snow clearing, de-icing of aircraft and in-terminal assistance for passengers," Pearson International Airport said in a statement.

WestJet issued a warning that flights could be cancelled or delayed to and from Toronto for the two days. Air Canada has issued similar alert that their flights could be impacted.

While many private schools have already decided to close down, some schools boards such as Peel, Halton, Durhan and York Region have asked parents to get update from their websites. The Toronto District School Board, however, had withheld their decision until Friday morning, CBC reported. 

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