Environment Canada has issued a warning of "significant heat and humidity" for Peel and Halton for Friday, July 19 and Saturday, July 20.

The agency is predicting temperatures in the low to mid-thirties with afternoon humidex values of 40 C or above during the heat warning, which effects Mississauga, Brampton, Halton Hills, Milton, Caledon, Burlington and Oakville.

Nighttime temperatures on Friday and Saturday are forecast to drop to the mid to low-20s. Cooler and less humid weather is anticipated on Sunday.

Environment Canada warns that extreme heat affects everyone and the risks are greater for children, pregnant women, older adults, people with chronic illnesses, and people working or exercising outdoors.