Environment Canada has issued a Heat Warning for Toronto ahead of an expected high between 30°C and 33°C on Tuesday and Wednesday.
And that is without the humidex.
It is expected to feel like 35°C in Toronto on Tuesday afternoon.
Overnight, low temperatures between 19°C and 22°C are called for, with a chance of a thunderstorm.
By Wednesday afternoon, humidex values are expected to reach 39°C, and a risk of thunderstorms remains throughout the day.
Temperatures should cool down by Wednesday night as a cold front passes through Southern Ontario, the weather agency says.
Heat warnings are issued when very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses, such as heat stroke or heat exhaustion.
The City of Toronto announced the following 14 Emergency Cooling Centres will open across Toronto during Heat Warnings:
• Metro Hall, 55 John St.
• East York Civic Centre, 850 Coxwell Avenue
• North York Civic Centre, 5100 Yonge Street
• Etobicoke Civic Centre, 399 The West Mall
• Scarborough Civic Centre, 150 Borough Drive
• Domenico Di Luca Community Recreation Centre, 25 Stanley Road
• Scarborough Village Recreation Centre, 3600 Kingston Road
• Amesbury Sports Complex (Arena), 155 Culford Drive
• Wallace Emerson Community Centre, 1260 Dufferin Street
• Regent Park Community Centre, 402 Shuter Street
• Malvern Recreation Centre, 30 Sewells Road
• Jenner Jean-Marie Community Centre, 48 Thorncliffe Park Drive
• Elmbank Community Centre, 10 Rampart Road
• Ourland Community Centre, 18 Ourland Avenue
All the centres will operate during Heat Warnings only, from 11 am to 7 pm, except Metro Hall, which will run 24 hours during Heat Warnings.