Hot and humid temperatures are expected to continue through Friday.
Environment Canada has issued a special weather statement for Sarnia-Lambton.
The national weather agency said a relatively hot and humid airmass over the area will result in daytime highs near 30 C (86 F) with humidex values in the high 30s.
We'll see a little relief during the overnight hours with lows near 20 C (68 F).
A stiff northerly breeze Wednesday, however, made it considerably cooler near Lake Huron, and had the Blue Water Bridge, Point Edward and the Sarnia lakeshore shrouded in fog.
A heat warning remains in effect for Chatham-Kent and Windsor-Essex.
Environment Canada said a cold front will move early Saturday morning bringing cooler temperatures and lower humidity in time for the weekend.