Sweltering summer has come early

Heat dome expected to cause 'dangerously hot and humid conditions' this week - even at night

- KEVIN JIANG

Swathes of the nation stretching from Ontario to Atlantic Canada are expected to bake under a prolonged heat dome this week - a prelude to another sweltering summer, meteorologists tell the Star.

In Toronto, Environment Canada issued a heat warning beginning Monday for "dangerously hot and humid conditions" expected to last through most of the week, with daytime highs of 30 to 35 C that feel more like 40 to 45 C with humidity.

Little relief will be found overnight, with temperatures hovering around 20 to 23 C, or 26 to 30 C near Pearson airport after accounting for humidity.

"It's the duration of this (heat dome), the added humidity and the intensity of the temperatures that make this particularly worrisome," David Phillips, a senior climatologist with Environment Canada, told the Star.

"This is not a one-off. We're still a month away from what typically is the warmest time of the summer," he continued, likening this week's phenomenon to a "dress-rehearsal for what we're going to be seeing more of this summer period."

What is a heat dome?

A heat dome is a massive bubble of "stagnant air" stacking up into the mid-to upper-atmosphere, explained Doug Gillham, a meteorologist with the Weather Network.