Environment Canada says conditions are ripe for "dangerous" thunderstorms this afternoon and this evening, that could bring sudden downpours and flash flooding in urban areas.
It could also produce wind gusts up to 90 km/h in isolated areas.
The weather authority issued a thunderstorm watch for Windsor-Essex and Chatham-Kent early Thursday afternoon, adding to the heat warning that's been in place for most of the week.
The thunderstorms will be isolated, said Environment Canada, but where the storms do land, they could bring upwards of 50 millimetres of rain in short periods of time.
That kind of downpour can cause localized flooding and water pooling, especially in parts of the city with poor drainage, said Environment Canada.
The storm system is expected to move past the region by early this evening. Environment Canada's hour-by-hour forecast shows no chance of showers after 9 p.m. tonight.
Meanwhile, Environment Canada said Thursday that the heat and humidity is showing signs of continuing into the weekend, and even the first part of next week.
It said that daytime temperatures could reach 32 C, with humidex values of up to 42. Overnight lows will be between 20 and 22 C.
According to Dave Phillips, a senior climatologist with Environment Canada, Tuesday's humidex value was higher in Windsor-Essex than it was in Tampa, Florida.