Heat warnings hoisted as prolonged hot, humid weather arrives
Some cities could see daytime highs push 30 degrees for four or five consecutive days
Summer is locking in across Eastern Canada as temperatures and humidity levels rise beneath a strong ridge of high pressure growing over the region.
The heat will build in southern Ontario, southern Quebec, and the Atlantic provinces, where multiple days of high temperatures in the 30s with even higher humidex values are in the forecast.
Humid heat affects everyone. Sensitive groups are especially vulnerable to heat-related illnesses, but even healthy folks are susceptible to heat exhaustion or worse in extreme heat.
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Temperatures rise this weekend into next week
The culprit behind this upcoming heat wave is a formidable ridge of high pressure building over the eastern half of the country. Southerly winds will pump excess humidity into the region, leading to the miserable combination of humid heat.
As of Friday evening, heat warnings were in effect for much of Ontario, as well as portions of western Quebec, eastern and northern Newfoundland, and portions of Labrador.
Numerous cities could experience four to five days with daytime high temperatures at or above 30°C, including Toronto, Ottawa, Montreal, and Fredericton.
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Humidity will push feels-like values into the upper 30s throughout much of the region, and possibly into the lower 40s for some spots.
Nighttime lows will provide little relief from the day's heat in the Greater Toronto Area (GTA), especially, where temperatures will remain in the lower to mid-20s.
According to Environment and Climate Change Canada (ECCC), humidex values above 40 occur on only one day per year in Ottawa. The upcoming stretch may result in two.
August in Toronto averages just more than six days with a humidex of 35 or higher. That threshold could be met in less than a week.
Why humid heat is dangerous
Sweat cools us off by wicking heat away from our skin as it evaporates. Humidity prevents our sweat from evaporating efficiently—the trapped heat causing our body temperature to rise. This can lead to heat-related illnesses such as heat exhaustion and heat stroke.
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Humidity also prevents nighttime lows from cooling off as much as normal, providing little to no relief from extreme daytime temperatures.
Day after day of high heat and humidity take a toll on those living without air conditioning, folks who have chronic illnesses, and the elderly.
Seek out air conditioning as much as possible, stick to the shade, stay well hydrated, and frequently check in with your vulnerable friends, family, and neighbours.