Tornado watches are in place for a large swath of central Ontario from the Bruce Peninsula to Ottawa, as a cold front sweeps into the province with storms that will lift the heat that has blanketed Ontario and Quebec over the past week.
People in the North Bay, Powassan, Mattawa area and West Nipissing-French River were briefly under a tornado warning Friday morning, but it has since been reduced to a severe thunderstorm warning.
A watch means conditions are favourable for storms, while warnings mean extreme weather is occurring or imminent.
There are severe thunderstorm warnings or watches across central and southern Ontario, including in Toronto, Sarnia, London, Peterborough and Kingston.
Montreal also sees the risk for severe weather today with a high of 33 C, feeling like 45 with humidex.
Heavy rain in storms could mean 40 millimetres in southern Ontario and as much as 60 mm in western and southern Quebec, with higher amounts possible in localized areas.
The Toronto area reached official heat wave status — three straight days of 32 C or higher — when a high of 33.7 C was measured at Pearson International Airport Thursday. Ottawa reached the same status by Wednesday.
In Mississauga, hundreds of residents of an apartment building were forced outside in the sweltering conditions early Friday after an electrical fire cut power to their building.
The Maritimes will also be muggy and unsettled Friday as humid air moves in with humidex values in the low to mid 30s, and a thunderstorm risk for New Brunswick.
- Read about humidex, the flawed Canadian way to calculate summer discomfort
Eastern Canada isn't alone in facing severe weather. In Western Canada, there is a risk of thunderstorms in large swath south of a line that extends from northeastern B.C. through Saskatoon to southwestern Manitoba.