Environment Canada has issued a heat warning for Sarnia-Lambton.
The weather agency says a hot and humid air mass over the American mid-west is expected to arrive on Friday and remain in place through the weekend.
Afternoon temperatures are forecast to be in the low 30s, with humidex values near 40 C.
Overnight lows will remain in the low 20s, providing little relief from the heat.
A cold front is expected to move into the region on Monday night, ushering in cooler temperatures and lower humidity.
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.
