Environment Canada says significant heat and humidity arrives Friday.
Daytime temperatures in the low to mid thirties with humidex values of 40 or higher are expected Friday and again on Saturday.
Little relief is expected Friday night and Saturday night as temperatures will only fall to the low to mid-twenties with humidex values remaining near 30.
A cooler and less humid air mass is forecast to arrive in the wake of a weak cold front Sunday.
Extreme heat affects everyone with the risks greater for young children, pregnant women, older adults, people with chronic illnesses and people working or exercising outdoors.
Never leave people or pets inside a parked vehicle.