Heavy rain and thunderstorms are possible Thursday.
Environment Canada has issued a special weather statement for Sarnia-Lambton.
The national weather agency said rainfall amounts of 40 to 60 millimetres are possible by Thursday night.
Environment Canada said some areas could see multiple rounds of thunderstorms throughout the day.
Heavy downpours can result in flash floods and water pooling on roads.
Localized flooding in low-lying areas is also possible.