Environment Canada has issued the heat warning, which is expected to last until Wednesday in some areas.
Hot and humid weather in the forecast with temperatures between 29 and 34 degrees C.
With the humidex, the national weather agency says the temperature could feel like anywhere between 35 to 40 in some areas.
There will be more “hot, uncomfortable weather that we’ve been experiencing already and we anticipate experiencing until at least mid-week,” says Steven Flisfeder, Environment Canada warning preparedness meteorologist.
With a cold front expected to come into the region later Wednesday, the weather agency says it will hopefully provide some relief from the heat.
“We’ll start to see a bit of reprieve Thursday, along with some rain showers and possible thunderstorms in the forecast for Thursday, and then finally, on Friday is when we expect to get back to normal temperatures for this time of year,” Flisfeder says.
The weather agency says daytime high temperatures will be very atypical of early September, with highs reaching 29 to 31 degrees C.
The weather agency warns people to be cautious in the heat to check on older family and friends.