Environment Canada has issued a special weather statement warning of the possibility of strong thunderstorms.
The statement covers Toronto, the GTA and much of Southern Ontario.
It says the worst of the storms are expected to hit Wednesday morning through midday with local rainfall amounts in the 30 to 50 millimetre range.
That will be followed by a heat wave to take us through the Canada Day long weekend.
Things start to heat up on Thursday, with an expected high of 28 degrees. Friday, they're calling for a high of 31 and by Saturday and Sunday; 36 degrees and humid.
The weather agency says it's unclear how long the heat will linger but, "current indications suggest the heat could persist into the middle of next week."