Environment Canada has issued a heat warning, that covers a wide area of the GTA and into Southern Ontario.
The weather agency says the high is expected to reach 32 degrees in Toronto on Friday, and the humidity will make it feel closer to 41 degrees in the afternoon.
Early Friday morning Toronto's Medicial Officer of Health also issued a heat alert.
Forecasters also warn that this type of extreme heat can put many at risk. Babies and young children, the elderly, and people with chronic breathing issues may want to limit the time spent outside.
Meteorologist Geoff Coulsen adds there's a cold front pushing up from Michigan, which will bring some showers and thunderstorms later in the day.
"There is the risk some of those storms could be severe" said Coulsen.
However, those storms will bring some relief from the heat in time for the weekend with a high of only 22 projected for Saturday.
A heat warning replaces the humidex advisory that used to be issued by Environment Canada.