Toronto in for an 'oppressive' heat wave next week

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The heat is on – and then some.

After some cooler than usual temperatures earlier this week and last weekend, the GTA is about to get blasted by an oppressive heat wave starting Monday and lasting until at least Thursday, says Doug Gillham, a meteorologist from The Weather Network.

“We’re quickly going from, ‘Where’s summer?’ which is what a lot of people have asked me this week, to next week which is not just summer (temperatures) but it’s going to be a heat wave,” he said.

“And likely some record-breaking heat and truly oppressive humidity that will give us humidex values in the low to mid-40sC, so that’s getting in dangerous heat category. It really starts Monday (afternoon) but it’ll peak Tuesday, Wednesday, Thursday, but by Monday we’ll likely see the humidex reach 40C and it should continue most, if not all, of next week.”

Gillham said on top of those temperatures, there won’t be much relief at night.

“The lows will only drop to the low to mid-20sC,’” he said. “You’ll start hearing the term heat dome. A larger ridge in the upper atmosphere. A larger ridge of sinking air. And we’ll also have the flow of air from the Gulf of Mexico. And we’re at the time of year where the sun angles the strongest so all those things coming together, the heat dome, this time it’s going to be centred over the southern Great Lakes. It’s going to give us this extended stretch of oppressive heat and humidity.”

Gillham said one reprieve is that it won’t be as hot along the water.

“Like on Toronto Island, versus what it will be north of the 401, 407 (highways),” he said. “It’s not like it’s going to be cool by the lake. It’s just going to be less not.”

Gillham said Canada’s east in general, the long-range forecast shows, will be having a hot summer due to a phenomenon known as La Nina.

“Looking back at years when we went from a winter El Nino to a quick shift to La Nina, the focus on the heat tends to be the U.S. Midwest and into the Great Lakes,” he said.

“Summer’s just getting started. We do think the extreme heat and humidity will relax. We don’t know exactly when the (cold) front will come through. During next weekend or the following week we should have a few days where it’s much more comfortable. But I think we’re back into hot weather before Canada Day so July will be hot.”

“This summer will be remembered for its heat. I don’t think we ever got this hot last summer,” Gillham said.