Environment Canada has issued a heat warning for Toronto as the GTA gets set for two days of sweltering and humid conditions to start the week.
Monday's high is set to reach 32 C under sunny skies, with the humidex making it feel like 39.
On Tuesday, the high is expected to hit 33 C with a humidex of 41.
Daytime highs will be in the low 30's. Normal daytime highs this time of year average 27 C at Pearson International Airport.
"Overnight low temperatures are forecast to fall to only 21 to 25 C, providing little relief from the heat," Environment Canada says.
Emergency cooling centres open in Toronto
The City of Toronto has now made eight Emergency Cooling Centres accessible to the public .
Two outreach teams will also do wellness checks, providing people outside with water and recommending that if they stay outdoors they should move to a shaded area, the city said in a news release.
The federal agency warns young children, pregnant women, older adults, people with chronic illnesses and those working or exercising outdoors face the greatest risk when it comes to negative health outcomes linked to the heat. That includes conditions like heat exhaustion or more seriously, heat stroke.
That weather brings with it the chance of thunderstorms. Environment Canada says some may develop late or overnight Monday, while that risk will linger through Tuesday.
The hot weather is expected to break by Wednesday, which has a forecast high of just 19 C. Rain is in the forecast for Wednesday and Thursday before the sun returns on Friday.
A large portion of Ontario is under a thunderstorm watch, with severe storms occurring in cottage country. In Toronto and the GTA, expect scattered thunderstorms with heavy downpours.