Parts of Huron-Perth and Grey-Bruce are under a special weather statement due to expected rainfall.
Environment Canada says rainfall amounts of 20 to 40 millimetres are expected with rainfall beginning overnight Tuesday and ending early Thursday morning.
The ground has limited ability to absorb further rainfall, the agency says.
Listowel, Milverton, northern Perth County along with Wingham, Blyth and northern Huron County are under the weather advisory.
The Bruce Peninsula, Sauble Beach, Tobermory, Hanover, Dundalk, southern Grey County along with Owen Sound, Blue Mountains and northern Grey County are under the advisory.
Southern Bruce County, including Saugeen Shores and Kincardine are also at threat for excessive rain.
The rainfall is associated with a Texas Low that will track across southern Ontario Wednesday and Wednesday night, Environment Canada says.
