Environment Canada had issued a severe thunderstorm watch for the GTA on Tuesday afternoon, but it was cancelled sometime after 8 p.m.
A severe thunderstorm warning was in effect for the Barrie, Innisfil, Angus, Collingwood, Orillia, Bracebridge, Gravenhurst.
The weather agency said conditions were favourable for the development of dangerous thunderstorms.
The thunderstorms could produce damaging wind gusts, large hail and torential rain.
Environment Canada says local rainfall amounts of 50 mm an hour were possible.