'Sleeping without air conditioning will be very uncomfortable,' Global News weather specialist Mike Arsenault said.

Environment Canada first issued the warnings at around 5:45 p.m. on Tuesday. As of 8 p.m., only Hamilton, Burlington and Oakville were covered under a severe thunderstorm warning.

"There is a possibility of flooding to occur near ravine areas and areas that are low lying and next to watercourses."

Global News chief meteorologist Anthony Farnell said it will be mainly sunny and dry in Toronto throughout the weekend until a cold front moves in Sunday night.

"It's the continuation of what has been a very hot July."

The remnants of Tropical Storm Fay could bring periods of intense rain to the Greater Toronto Area on Saturday even though the system is tracking farther east.

"A special air quality statement is in place due to the possibility of deteriorating air quality," the agency wrote in a press release Thursday. "Hot and sunny conditions are expected to cause increasing ground-level ozone concentrations in the area."

A tornado watch was also issued briefly for Toronto Wednesday afternoon.

"It is shaping up to be one of the hottest Julys in recent memory for southern and central Ontario."

City officials said beginning at 11 a.m. Thursday, 15 emergency cooling centres will be opened for the duration of the heat warning.