Environment Canada has issued a special weather statement for Toronto and the GTA, due to several low-pressure systems that are hanging over Southern Ontario.
The long weekend began with heavy rain pounding down on the city on Friday morning.
The biggest concerns resulting from the system are near area rivers and streams, where water levels are expected to be higher than normal.
The Toronto and Region Conservation Authority says riverbanks could be slippery and unstable, and is reminding to people to keep children and pets at a safe distance.
Another concern is flooding and ponding on area roads overnight Friday and into Saturday.
Parts of the Lakeshore near the Exhibition grounds experienced flooding Friday afternoon, with cars hydroplaning along the curb lanes.
The heaviest downpours are forecast for Friday night when rainfall totals could top out at 25 to 50 millimetres.
The rain should taper off on Saturday, with warmer, drier conditions forecast for Sunday.
- With files from Priya Sam