The Essex Region Conservation Authority (ERCA) has advised that Wednesday's weather may result in swollen bodies of water.
A flood outlook is in effect.
ERCA Watershed Management Services Director James Bryant said some areas received up to 30 millimetres of rain in a round of storms Wednesday afternoon, and more is coming.
"Forecasts are predicting risks of more convective thunderstorms within the next 24 hours," said Bryant. "Such storms have the ability to appear suddenly with little warning and can sometimes result in 25 millimetres, or one inch, or more, in a very short amount of time, coupled with high winds. Should we receive any such convective storms, it should be expected that smaller watercourses will rise quickly and that low-lying areas have moving or standing water."
Residents living or travelling near elevated water levels are urged to exercise caution. Fast-moving water and slippery banks may become hazardous.
The outlook is active until at least 6 p.m. on Thursday, but ERCA will update as conditions warrant.