As much as 40 mm of rain could fall across the Grand River watershed by Tuesday.
The Grand River Conservation Authority says that much rain, combined with warm temperatures that will melt much of the remaining snow, could lead to flooding.
Flood warnings have been issued for parts of Cambridge, Brantford and Cayuga.
As an ice jam remains in the river in Cambridge, it is possible that flooding will occur in areas not normally prone to it.
Specifically, the GRCA is warning of potential flooding near the Grand in the Blair area, and near the Speed River downstream of the King Street bridge in Preston.
Blackbridge Road, which is often one of the first streets in Cambridge to flood, could be closed if water levels rise and the road floods out.
Gilkison Street in Brantford is already closed near the river and is expected to remain closed until water levels start to recede.
Downstream in Cayuga, the GRCA says, ice jam flooding could affect the floodplain from Monday evening through Thursday.
The remainder of the watershed is under a flood watch, with officials warning of potential flooding in low-lying areas. The GRCA says anyone in an area normally prone to flooding should keep an eye on water levels and take necessary precautions.
Other roads that could be closed based on current projections include Highway 25 in Grand Valley and the low-level bridge on Three Bridges Road near St. Jacobs.
In addition to Cambridge and Cayuga, the GRCA says ice jams are in place in the Grand in Conestogo and Brantford, as well as in the Nith River downstream of Plattsville.
The ice jams were considered stable as of Friday, although conditions could change rapidly as temperatures warm.
“It is not possible to predict if ice jams will release during this event (but) the potential for flooding at the location of these ice jams exists,” the GRCA said in a statement.
As of Friday, Environment Canada’s forecast for Waterloo-Wellington was calling for highs of 7 C on Monday and 8 C on Tuesday, accompanied by significant rainfall both days.
