Environment Canada has put a special weather statement into effect for parts of Bruce county.
The Bruce Peninsula, Sauble Beach, and Tobermory could see 25-50 mm of rain begin on Monday afternoon and last into Tuesday afternoon.
Some areas may see even higher amounts of accumulation alongside thunderstorms.
"There is some uncertainty with the track and timing of a low-pressure system and associated cold front that will move across the area," the weather agency said "Hence exact timing and total rainfall amounts are subject to change."
Anyone concerned about flooding is urged to consult their local conservation authority or visit Ontario's flood information webpage.