Extreme, prolonged heat wave expected to cover much of Ontario, parts of Quebec

A blast of dangerous heat has settled over Ontario and southern Quebec, with the extreme temperatures expected to linger for several days as tens of thousands of people are set to gather for Canada Day and World Cup festivities.

Environment Canada warns the hot and humid conditions could last through the weekend in some areas.

“I’m a little bit uncomfortable confidently predicting an end to the heat wave because it looks like we could see heat persisting even into next week as well,” said Peter Kimbell, a warning preparedness meteorologist with the weather office.

“It’s going to be very, very hot and very muggy as well, and dangerous for many people.”

Temperatures are expected to hover around the low- to mid-30s for much of the week across southern Ontario and Quebec. The humidity is expected to make it feel about 10 degrees hotter.

The hottest days in Toronto are expected to coincide with Wednesday’s Canada Day celebrations and Thursday’s FIFA World Cup knockout match between Croatia and Portugal.

The nights will offer little relief, with the lowest temperatures still expected to top 20 degrees.

Dr. David Kaiser of Montreal Public Health said that those planning to celebrate Canada Day should limit their alcohol consumption as it increases dehydration and raises the risk of heat-related illness like heat stroke. He also warned that some medication, including for mental health, heart conditions and hypertension, can affect how the body reacts to heat.

July 1 is also traditionally moving day in Quebec, since that’s when most leases in the province expire.

For those planning to move, Kaiser said they should start either as early as possible or wait until later in the afternoon to avoid doing heavy lifting outside during the hottest part of the day. He stressed that taking regular breaks, drinking a lot of water and staying in the shade is crucial.

“There’s really no magic solution to moving day, you know, looking at 40 degrees humidex tomorrow, but there are some measures that at least can avoid the most important exposure,” he said.

Kaiser also urged Montrealers to look out for people who are homeless.

“You see someone who doesn’t seem to be well, the minimum is to ask if they are OK. If we are not reassured by asking the question, I think the right reflex is to call the emergency services, they are there for that,” he said, adding that people with access to air conditioning should help others.

“People who have the privilege to protect themselves from the heat, how do we take care of others? We see what’s happening in Europe at this time, and we know that in Montreal — and we’ve already seen it for a few years — these episodes will be more frequent and more severe in the years to come.”

This report by The Canadian Press was first published June 30, 2026.

–By Erika Morris in Montreal and Jordan Omstead in Toronto

Canadian Press Staff, The Canadian Press