Environment Canada has issued a Special Weather Statement for Perth County.
The weather agency says significant rainfall is expected to begin Tuesday evening.
The rain will last into Wednesday and may continue in some areas through Wednesday night as well.
Some areas could see 70 to 100 millimetres of rain by Thursday morning.
Meteorologists says there is still considerable uncertainty and variability in the forecast with both the location of the heaviest rain and the duration of the rainfall event.
Rainfall Warnings will likely be issued for some areas as the event draws nearer.
