The Collingwood and Wasaga Beach area is now under a flood warning.
The Nottawasaga Valley Conservation Authority says the potential for flooding and ice jams is high.
The NVCA says rain and above freezing temperatures will result in significant runoff and the rising flows will create a high risk for ice jam flooding with very little warning.
Areas of concern are the middle and lower Nottawasaga River, the Blue Mountain waterways and the Mad River in Creemore and Avening.
The NVCA says its warning will stay in effect until further notice.