Travellers flying in and out of Toronto's Pearson International Airport are contending with several cancellations and delays caused by stormy weather that rolled through southern Ontario on Tuesday.

Forty-five arriving flights and 31 departing flights have been cancelled since the the start of Wednesday. Dozens more were cancelled or delayed Tuesday afternoon, when flights were grounded for three hours due to heavy rain and lightning.

The ongoing delays and cancellations on Wednesday are a result of having to clear through the backlog caused by Tuesday's weather, said Greater Toronto Airports Authority spokesman Scott Armstrong.

Scores of travellers were stranded at the airport overnight because of the delay.

"We have extra staff on hand. We are handing out water to people who have been stuck here overnight," he said.

Armstrong had said they hoped things would return to normal by early afternoon, but as 4 p.m. there were still dozens of delays and more than a dozen cancellations.

Armstrong recommends that those who have a flight scheduled for today should call ahead or check online to see if it's on time.