A winter storm making its way toward southern Ontario has prompted WestJet to cancel all flights in and out of Toronto Pearson International Airport on Friday.

The airline made the announcement on Thursday evening.

“WestJet has proactively cancelled all scheduled flights arriving and departing Toronto Pearson International Airport (YYZ) beginning at 9:00 a.m. EST on Friday, December 23 until end of day, with a restart dependent on weather conditions by Saturday, December 24,” the advisory read.

WestJet said the service suspension would also impact airports in Ottawa, London, Waterloo and Montreal. In total, the cancellations will affect about 140 flights across the five airports.

“The prolonged and extreme weather events that continue to impact multiple regions across Canada are unlike anything we’ve experienced. With the additional storms forecasted for British Columbia, Southern Ontario and Quebec, we are taking a proactive and measured approach to protect our operations and prioritize recovery flying this weekend,” said Diederik Pen, WestJet’s chief operations officer, in a statement.

“The decision to stand down more flights is extremely difficult, but it is necessary, so that we can be best prepared to safely fly as many guests, with as little disruption as possible when the weather improves.”

WestJet has also cancelled hundreds of flights in British Columbia as a significant winter storm is also hitting that province.

The airline said 1,044 flights had been cancelled since Dec. 18.

The Greater Toronto Airport Authority (GTAA), which operates Pearson airport, advised travellers to check the status of their flights with airlines.

"Today's travel volumes at Pearson were as expected, and we've planned accordingly throughout the weekend; however, airlines remain affected by the weather over Western Canada and the U.S. and are still working to recover their operations," the GTAA said in a statement.

"It is critical during the holidays that our partners continue to make every effort to address staffing provisions and crew allocations to deal with ongoing weather disruptions."

Toronto and the rest of southern Ontario are bracing for a major winter storm that is expected to bring rain, snow, strong winds and frigid temperatures. Environment Canada has issued a winter storm warning for the region.

The storm has led schools in the Greater Toronto Area to close on Friday.