Sarnia-Lambton could be drenched by up to two inches of rain by Friday morning.
Environment Canada issued a special weather statement Thursday saying 30 millimetres to 50 millimetres of rain is possible with the potential for even higher amounts in thunderstorms.
Rain, heavy at times, is expected Thursday afternoon, Thursday night and into Friday.
Motorists are advised to watch for ponding on area roads.
The St. Clair Region Conservation Authority issued a flood outlook Thursday in anticipation of heavy rain Thursday into Friday and again Sunday.
The conservation authority said increased runoff and flash flooding are possible as well as storm surge along the Lake St. Clair shoreline due to strong south-southwesterly winds.
The winds may cause a backwater effect in the Wallaceburg area, slowing the flow of water out of the Sydenham River and contributing to elevated water levels.
Residents are reminded to avoid watercourses and flooded areas due to slippery banks and cold, swift-moving water. Children and pets should be kept away from the water.
