A special weather statement has been issued for Niagara warning of heavy downpours.
Environment Canada says showers with the risk of thunderstorms could give rainfall amounts of 30 to 40 mm in the region today.
Localized flooding in low-lying areas is possible. Up to marble size hail is also possible.
Niagara Falls has already been hit with hail.
The chance of showers and thunderstorms continues into the overnight hours.