The national weather agency says the storms are "capable of producing very strong wind gusts, pea to dime size hail and heavy rain."

Environment Canada warns it will feel like 44 degrees in Montreal.

Wild summer weather rolled through Edmonton and much of central Alberta Thursday night, bringing with it heavy rain, lighting and thunder.

The forecast is also warning of the risk of thunderstorms on Friday and of the possibility of rain throughout the weekend and into Monday.

"A special air quality statement is in place due to the possibility of deteriorating air quality," the agency wrote in a press release Thursday. "Hot and sunny conditions are expected to cause increasing ground-level ozone concentrations in the area."

A tornado watch was also issued briefly for Toronto Wednesday afternoon.

Environment Canada is warning residents in the greater Montreal area to watch out for severe thunderstorms this Wednesday afternoon and early evening.

Daytime high temperatures that are more than 30 C are expected, with humidex values predicted to be in the high 30s to low 40s.

As Montreal continues to deal with the smouldering heat wave, the workers' health and safety board is issuing warnings to local contractors working outdoors.

Cities around the Hamilton-Niagara region have opened up cooling centres to avoid the onset of heat-related illnesses.