Thunderstorms moved across the region in the midst of a multi-day heat event on Tuesday afternoon.
Environment Canada issued a severe thunderstorm warning for Sarnia, Petrolia, and west Lambton shortly after 2:30 p.m. The warning lifted shortly before 4 p.m.
The national weather agency said the storms were capable of producing strong wind gusts and heavy rain, which may cause flash flooding and reduced visibility.
About 50 millimetres of rainfall was anticipated.
The heavy rain and thunderstorms came while a heat warning was in effect for the region.
A cooler air mass has brought an end to the extreme heat, and the warning was lifted early Wednesday morning.