As of 11 a.m. on Sunday, Environment Canada reported the temperature being –22 C at Toronto Pearson International Airport. With the windchill, it felt more like –38.
The airport advised it passengers to check the status of their flights before proceeding to Pearson.
In particular, Boston-bound flights were being "severely impacted by winter weather," according to a tweet from the @TorontoPearson account.
The city was already under an extreme cold weather alert ahead of Sunday. It was extended, due to the severe cold.
Police and city officials were reminding people in Toronto to look out for their fellow residents.