Southwestern Ontario is in for some rain, followed by extreme heat.
Environment Canada has issued a special weather statement for the region, including London, Middlesex County, Elgin County, Oxford County, Chatham-Kent, and Windsor-Essex. The weather agency says there is the potential for heavy thunderstorms Tuesday night and into Wednesday, followed by an extreme heat event for the Canada Day long weekend.
The heaviest storms are expected very early Wednesday morning through midday. Total local rainfall amounts could be in the 30 to 50 mm range, with higher amounts possible under the heaviest storms.
"A persistent southwest flow is then forecast to develop, bringing hot and humid air from the Gulf of Mexico," the statement says. "Beginning Friday or Saturday and continuing through the Canada Day long weekend, expected daytime highs are in the low to mid thirties with humidex values into the mid forties. Overnight low temperatures will only fall to the low twenties, providing little or no relief from the heat."
Officials say there is still uncertainty regarding when the heat event will come to an end. Current indications suggest the heat could persist into the middle of next week.
This will likely be the most significant heat event of the season thus far. Environment Canada says heat warnings will be issued as the event draws nearer.