The St. Clair Region Conservation Authority (SCRCA) has issued a flood outlook because of above freezing temperatures and heavy rainfall.
It said a Texas low followed by a second low pressure system is forecast to bring warmer temperatures and rainfall in two waves over the next five days.
The SCRCA said rain showers of approximately two millimetres are expected Friday afternoon and will continue overnight. A further one millimeter is forecast for Saturday.
On Sunday, a further 20 to 30 millimetres is forecast across the watershed with the potential for higher amounts in localized areas.
An additional five to 10 millimetres will fall on Tuesday.
The conservation authority said the majority of the rainfall will fall on Sunday and Tuesday.
Daytime temperatures will also be higher than seasonal with overnight lows remaining mild.
The SCRCA warns snowpack depths of 10 centimetres will degrade with the warm temperatures and rain. This will lead to increased runoff and watercourses.
Ponding is likely to occur in low-lying areas as soils become saturated.
The SCRCA said water levels are likely to respond quickly to the increased runoff and will be elevated and may lead to minor flooding into natural floodplain areas.
Individuals are reminded to avoid watercourses and flooded areas because of dangerous conditions, slippery banks and swift moving water.
Children and pets should be kept away from the water.
The flood outlook will be in effect until January 2, unless it is updated.