Environment Canada has issued a rainfall warning for Sarnia-Lambton.
The national weather agency said total amounts of 20 to 35 millimetres are possible starting late in the day on Friday.
It said periods of rain will continue Friday night and become heavy at times through Saturday. Rain is expected to come to an end Saturday evening.
Meanwhile, the St. Clair Region Conservation Authority issued a flood outlook Thursday afternoon, advising residents to be cautious near river banks and fast moving water.
We're being reminded that heavy downpours can cause flash floods and water pooling on roads.
UPDATE: At 2:41 p.m. on Saturday, the rainfall warning ended for all municipalities throughout Sarnia-Lambton.