Heat dome to act like 'lid of a barbecue' over London this weekend

Highs of between 33 and 34 degrees Celsius are expected in London this weekend, according to Environment Canada.

Record high temperatures expected in London over Canada Day weekend

The extended period of high heat could also lead to poor air quality, according to Environment Canada. (Jose A. Bernat Bacete/Getty Images)

A heat dome will descend on southwestern Ontario this weekend, like "the lid of a barbecue," according to Environment Canada. 

The city has already had a hot spring: we've had six days this year with temperatures above 30.

This weekend will be much worse, with the forecast calling for a record-breaking high of 34 on Saturday and 33 on Sunday. 

"Never has there been a warmer June 30 then in London," said Dave Philips, senior climatologist with Environment Canada, adding that the previous high of 33 dates all the way back to 1964.

There won't be much relief when the sun goes down. Nighttime temperatures that usually hover around 14 will instead be around 24.

"It's very sultry, and I'm talking about shaded temperature," Philips said. 

"The sun can add another 7 or 8 degrees to your skin, so it's quite lethal temperatures that we're talking about here."

The length of the heatwave is also dangerous, Philips said. One or two days of heat is one thing, but it's harder for the body to recover from the multiple days of heat that are expected in London.

Things will cool down — so to speak — to around 29 degrees on Tuesday. 

"We could go a whole week or ten days with temperatures in the very high 20s or mid to low 30s," without even factoring in humidity, Philips said.

The extended period of high heat could also lead to poor air quality, because the sun "cooks" chemicals in the air, and a lack of ventilation keeps them there.

Nowhere to run to, nowhere to hide

Philips said driving out of city limits won't necessarily lead to relief. The Grand Bend and Lake Huron area may be slightly cooler—but only by a degree or two, Philips said.

"It's a matter of grinning and bearing it," he said, adding that the weekend would be a good time to see a movie indoors, and to put off chores for another week.

Anyone who is caring for infants or elderly people should make sure to check in on them more frequently, Philips said.

He also recommends:

  • Drinking water or occasional sports drinks.
  • Avoiding caffeine and alcohols.
  • Using fans, air conditioning or sponges with cool water.

The Middlesex-London Health Unit issued a heat warning on Thursday.

A list of cooling centres is available online.