A heat warning is in effect for Windsor-Essex and Chatham-Kent.
Temperatures could reach more than 40C Sunday with the humidex Sunday, according to Environment Canada.
Overnight temperatures are expected to sit around 30C with humidity, providing little relief from the heat.
Environment Canada says the heat wave will carry through Monday before a cold front comes through the region Tuesday morning.
The UV index is also expected to be extremely high for the remainder of the weekend.