Snow, sleet, ice and freezing rain have hit the Greater Toronto Area, threatening to cause problems on one of the busiest travel days of the year.

Environment Canada has issued a freezing rain warning for much of southern Ontario, including London, areas around Georgian Bay and extending east to Kingston.

"The next few days are not looking good for travel," CBC meteorologist Claire Martin reported Friday.

In some areas north of the band of freezing rain, the precipitation will fall as snow.

"It's not like you can avoid certain highways and hope that they'll be dry and fine," said Martin. "You're into snow to the north of this system and rain to the south. So it's going to be messy for Friday."

On Saturday there's a chance of flurries in the forecast. On Sunday a second system of weather will arrive that Martin is calling "round number two" when forecasts are calling for a mix of snow, freezing rain and some rain.

The Ontario Provincial Police say travellers heading out on the highways will have to pay attention to road conditions, slow down and leave extra time to reach their destination.

Busy day at Pearson airport

At Pearson airport CBC's Linda Ward reported that travellers were in high spirits despite some long lines. Friday is projected to be the busiest travel day of the season at Pearson, with about 115,000 passengers expected.

On Friday morning the GTAA website listed some 100 delays and cancellations, most involving short-haul flights in Ontario, though some U.S. flights are also affected. Passengers are advised to check their flight status before heading to the airport.

"Terminal One is already filling in with people trying to get to their holiday destinations," reported Ward. "And we are seeing some delays and cancellations."

Air Canada and WestJet are warning passengers of further delays on Saturday if the weather worsens. Air Canada has also waived fees for passengers who change their flight plans due to weather.

"Even with these delays travellers are moving through the check-in lines quite well, most seem to be well on their way," Ward reported.