The heat goes on in southern Ontario and southern Quebec Thursday, with humidex values in the high 30s and low 40s.
CBC meteorologist Jay Scotland said temperatures should be slightly less warm than Wednesday, but still hot and humid.
Ottawa officially reached heat wave status yesterday — three straight days of 32 C or higher — and Toronto could follow suit today after a high of 34.8 C on Wednesday. The temperature was already 27 C in Toronto's downtown as of 7 a.m. ET.
"That would be seasonal average for a daytime high, and we're nowhere near the daytime high just yet," Scotland said. By 10 a.m., it was 31 C.
Montreal should see highs below 30 C, but it will still feel in the high 30s with the humidex, Scotland said. There is a high heat and humidity warning in place for parts of southern Quebec, including Montreal.
The humidity fuelled strong thunderstorms from eastern Ontario to New Brunswick yesterday, leaving as many as 60,000 customers without power in Montreal. About 8,100 Hydro-Quebec customers were still without power as of 7 a.m.
With a cold front approaching, the same possibility for storms exists today, especially for Ontario, Scotland said. There is a severe thunderstorm watch in effect for the Bruce Peninsula.
Quebec health officials said on Wednesday that they are investigating two deaths that may be connected to the heat.
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Officials urged anyone caught in the heat to drink lots of water and, if possible, seek relief in a local cooling centre, or an air-conditioned spot such as a movie theatre.
Scotland said the heat will break by the weekend.
Hot weather has also affected the U.S. this week, with the country's largest heat wave of the summer stagnating over large regions, bringing sizzling temperatures from South Dakota to Massachusetts.
With files from The Associated Press