Heat wave to grip Ontario, Quebec this week as humidex climbs into 40s

TORONTO — The first major heat wave of the summer is settling over parts of Ontario this week, with sweltering conditions expected to last for days and humidex values climbing into the 40s.

Parts of southwestern Ontario are under a yellow warning for heat through Friday, and possibly into the weekend. Environment Canada says the humidex could reach 42 today and climb as high as 45 by midweek.

A special weather statement is also in effect for parts of southern Quebec, where daytime highs are expected to reach 30 to 33 C, with humidex values between 40 and 44. The agency warns of a risk of heat exhaustion and heat stroke.

In Toronto, temperatures are set to climb above 30 C for at least the next six days.

“This one has the intensity and the duration to make it quite serious,” says Environment and Climate Change Canada climatologist David Phillips.

For anyone planning to attend outdoor events on Canada Day, it will be a hot one. The air temperature in the city is expected to hit 35 C and feel closer to 40 C with the humidex.

Overnight lows in Toronto as of Tuesday won’t dip below 23 C until the weekend, making for difficult sleeping conditions for those without air conditioning.

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Officials are urging people to watch for the early signs of heat exhaustion, which can include headache, nausea, dizziness, thirst, dark urine and intense fatigue. They are also asking people to check on older adults, those living alone and others at risk.

‘Extreme heat is dangerous’

Dr. Christopher Labos, an epidemiologist and cardiologist, said the danger should not be underestimated.

“I think people need to remember that extreme heat is dangerous, especially to older individuals, especially to people with pre-existing medical problems,” he said.

Labos said the best strategy is to avoid going outside, particularly during the daytime.

“This is not the time to go outside running. This is not the time to do your gardening. This is not the time to do outside work around the house,” he said. “You really should try to stay somewhere that is cool.”

• How to deal with heat exhaustion and heat stroke

He added: “People die of heat stroke. That’s why we’re seeing the spike in mortality we’re seeing now across Europe.”

Western Canada has already had a taste of summer, with temperatures reaching the mid- to high 30s across the region in June.

Meanwhile, a dangerous heat wave is set to grip a large swath of the United States, from Minnesota to the Gulf Coast. In North Carolina, the air temperature could top 40 C.