CBC meteorologist Michelle Leslie said that a risk of thunderstrorms existed for the city on Monday evening, after a day during which the mercury hit 34 C.
"There is the risk for thunderstorms that could approach severe limits, even for us here in the GTA until about 10:00 p.m. this evening," Leslie said.
Environment Canada issued a severe thunderstorm watch for Toronto on Monday evening, which warned of the "potential development of severe thunderstorms with large hail, damaging winds or heavy rainfall."
Leslie said that a cold front will move through the area overnight, which will bring about a change in winds for Tuesday.
It will feel cooler outside, with an expected daily high of about 27 C.
"A quiet day in the forecast tomorrow, no rain in sight for Tuesday," she said.
Yet another heat alert
On Monday the city issued yet another heat alert as the temperatures crept into the mid-30s.
Toronto has issued nine heat alerts and nine more extreme heat alerts since the summer began.
Environment Canada predicted that the high for Toronto on Monday would be 34 C, but would feel closer to 40 C with the humidity factored in.
As of 2 p.m. Monday, the temperature stood at 34 C at Pearson International Airport. It hovered in that range throughout the rest of the afternoon and early evening.
The same heat was being felt west of the city in Peel region, where the temperature reached 34 C in Brampton, Mississauga and Caledon.
In Markham, Richmond Hill and Vaughan, the mercury hit 33 C by the mid-afternoon, which was slightly warmer than Pickering, Oshawa and Whitby, all of which hit 31 C.
Toronto and much of southern Ontario are also under a humidex advisory.