Residents of Sarnia, Petrolia, Western Lambton County, Chatham-Kent, Leamington, Windsor, and Essex County could see severe thunderstorms Wednesday evening.
Environment Canada issued a severe thunderstorm watch just before 6 p.m., calling conditions favourable for storms capable of producing strong wind gusts, hail, and heavy rains.
The weather agency said areas could see between 30 mm and 50 mm of rainfall per hour and winds could reach 90 kilometres per hour.
"Damage to roofs, fences, branches or soft shelters is possible," a release said.
Flash flooding and reduced visibility are also possible.
The watch is in effect through Wednesday evening.