By Friday or Saturday, expect to see daytime highs into the mid-30s, though in some places it will feel more like somewhere in the mid-40s. Environment Canada says heat warnings will be issued as the event draws nearer.
Environment Canada has issued a special weather statement for Ottawa, warning of an "extreme heat event" for the Canada Day long weekend.
The heaviest storms are expected Wednesday morning and early afternoon. Low temperatures overnight are expected to be in the high teens to low-20s providing little relief from the heat.
The showers and thunderstorms forecast for Wednesday are forecast to give way to a persistent southwest flow, bringing hot and humid air from the Gulf of Mexico.
"Current indications suggest the heat could persist into the middle of next week", the special weather statement says.
It will be a hot and humid Canada's 151 birthday party in Ottawa.
Southwestern Ontario is in for some rain, followed by extreme heat.
The Canada Day weekend promises to be a hot one, folks.
While public activities set for Canada Day are scheduled to proceed as planned, the city says residents should plan to attend the festivities during cooler parts of the day.
The heat wave was a definitive sign of the arrival of summer in the Maritimes, just weeks after frost caused widespread damage to crops throughout the region.