Flights are slowly taking off at Pearson International Airport after days of extreme cold but broken water mains are in store for Toronto as the city enters a freeze-thaw cycle.

The city cancelled its extreme cold weather alert on Thursday afternoon and warm temperatures are in store for the weekend, but the weather was still causing problems across Toronto.

Dozens of flights have been cancelled at Pearson in both arrivals and departures. Click here to see if your flight is affected. The backlog began Tuesday, when extreme cold triggered a ground stop, meaning planes were unable to land at the airport. The cold caused equipment to freeze and safety issues for employees. Flights are now resuming.

Air Canada is warning passengers in parts of Canada and the United States to expect more flight cancellations and delays. The alert covers Pearson, Billy Bishop Airport, Montreal’s Trudeau International Airport and airports in Ottawa, St. John’s, N.L. and Halifax.

It also covers U.S. airports in Boston, Chicago, Cleveland, New York, Philadelphia and Washington.

A broken water pipe at St. Clair Station caused subway trains to bypass the station on Thursday morning. The station was closed for over an hour and has since reopened. However, the TTC says the Scotiabank Plaza entrance to the station remains closed.

By 6 a.m., three broken water mains had already been reported.

One was on Ralston Avenue, near O’Connor Drive and Woodbine Avenue. Another was seen on Queen’s Park Crescent north of College Street.

The TTC said a broken water main at Windemere Avenue and The Queensway caused the 77 Swansea bus to divert from its regular route.

Water main breaks are often caused by rapidly fluctuating temperatures. The freeze-thaw cycle damages the underground pipes, causing them to burst.

There’s a high of -6 C in the forecast for Thursday and a low of -8 C, 680News meteorologist Jill Taylor said. It will be a mostly sunny day with flurries arriving overnight.

The city could even see some rain as the weather warms up this weekend. There’s a high of 7 C on Saturday, Taylor said.

The TTC tweeted some incredible photos of the damage St. Clair Station. What was it like in your area? Send us your photos.

With files from The Canadian Press