Canada braces for week-long heat wave, experts warn of deadly potential

Canadians should prepare for a week-long heat wave, with experts urging serious attention to the potentially deadly conditions. Environment and Climate Change Canada (ECCC) warning preparedness meteorologist Jean-Philippe Chenier emphasized the importance of taking the heat wave seriously, noting its potential to be fatal.

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We’ve seen worse, when we have a duration longer than three days, but it’s very important to take this heat wave seriously.

The scorching temperatures are caused by a heat dome, a phenomenon where high atmospheric pressure traps heat and humidity. Chenier explained that this is due to hot air from the central U.S. combined with moisture from the Gulf of Mexico, a common pattern for heat waves in southern Ontario and Quebec.

Severe thunderstorms are also anticipated alongside the heat in northern and eastern Ontario and southern Quebec. While most provinces and territories have yellow heat alerts, signifying moderate but potentially disruptive impacts, Quebec is under an orange air quality warning, and parts of British Columbia are experiencing fog advisories.

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We have very hot air coming from Texas and central U.S., along with humidity coming from the Gulf of Mexico. So, this is the reason, but this is a classical setup for a heat wave in southern Ontario, as well as in southern Quebec.

Southern Quebec could see humidex values reach 40 to 44 from Wednesday through Saturday, with slight relief expected by the weekend. Southwestern Ontario faces a "high impact" yellow alert, with daytime highs of 30 to 36 degrees Celsius until Friday or Saturday, and overnight lows between 21 and 25 degrees. Humidex values in this region are expected to range from 37 to 45.

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In southern Quebec, we could see humidex is as high as 40 to 44 from Wednesday right through to Saturday and only seeing a little bit of relief later in the weekend.

Alberta is also under wider yellow alerts, classified as "moderate impact," with daytime highs between 29 and 31 degrees Celsius and overnight lows near 14 degrees, though cooler conditions are forecast by Thursday. The Greater Toronto Area, in particular, is expected to experience mid-week highs in the mid-30s, with humidex values in the 40s, marking what could be the first prolonged heat wave for many areas.

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The main front of the heat will be a focus on southern Ontario, where across the GTA we’re going to see temperatures into the mid-30s, especially mid-week Wednesday, Thursday in particular, with humidexes into those 40s.