Huron, Perth, Bruce, Grey and northern parts of Wellington County are being lumped into a special weather statement.
Environment Canada says much of the region is expected to receive significant amounts of rain.
A low pressure system is arriving Saturday and will spread rain across Southern Ontario from west to east through the day. In a lot of areas the rain will continue through Sunday afternoon and may be heavy at times.
There is also a risk of isolated thunderstorms on the weekend.
Regions from Windsor to the Golden Horseshoe will likely receive significant amounts of rain in the 30 to 60 millimetre range.
Easterly wind gusts could reach 50 to 70 km/h.
