Hundreds of flights have been cancelled at Pearson International Airport as a winter storm continues to hammer the city and the region.

As of 3 p.m., a total of 270 departing flights and 251 arriving flights had been cancelled. The number of cancellations represents about a third of all flights, according to numbers from the Greater Toronto Airports Authority.

“The best thing to do before you head out to the airport, check your flight information. Just make sure that you have the correct time and just take your time on the roads too,” GTAA spokesperson Shabeen Hanifa told CP24 earlier in the day. “We’ve got carefully designed winter operations that helps minimize the impact of that winter weather. Our focus is just moving people safely and efficiently.”

In addition to disrupting air travel, the storm is also impacting college and university campuses in Hamilton, Halton and the Niagara Region.

Sheridan College, Brock University, Mohawk College and McMaster University are were closed Tuesday morning in anticipation of heavy snowfall.

Hamilton, Burlington and Oakville were also under a winter storm warning on Tuesday and Environment Canada said the weather system was expected to bring a total of 20 to 30 centimetres of snow to the region by Tuesday night. A winter storm warning remains in effect for Niagara Region.

Toronto is expected to see significantly less snow, with five to 10 centimetres in the forecast today.

Environment Canada is warning drivers to allow extra time to get to your destination today due to potentially hazardous driving conditions.

“Strong and gusty northeast to north winds will whip up the freshly fallen powdery snow resulting in occasional blowing snow in exposed areas,” the national weather agency’s advisory read. “Untreated roads may be snow covered and slippery.”

OPP Sgt. Kerry Schmidt said there hasn't been an increase in the number of collisions in the GTA yet.

"So far, it looks like mostly just a dusting of snow," Schmidt said.

Trevor Tenn, the manager of road operations for the City of Toronto, said salt trucks have been out on the streets since Monday.

"We’ve got patrollers. We are monitoring the conditions every minute," he said.

The snow is expected to taper off on Wednesday morning as the weather system shifts away from the region.