Environment Canada warns conditions are favourable for severe thunderstorms on Saturday.
A severe thunderstorm watch was posted just before 12:30 p.m. for Sarnia-Lambton, Windsor-Essex and Chatham-Kent.
The weather agency said thunderstorms could develop in the afternoon and move into the evening.
Severe wind gusts and heavy down pours are possible.
Forecasters warn there could be local power outages.
Emergency Management Ontario recommends if threatening weather approaches to go indoors immediately.
Severe thunderstorm watches are issued when conditions are favourable for the development of thunderstorms capable of producing large hail, wind or rain.
