Older people, children and others at increased risk of heat-related illness are urged to take extra caution during a "multi-day" heat wave alert issued for Ontario.
Environment Canada said the heat warning is expected to last until Thursday for most of the province, including the Greater Toronto Area.
It said the actual temperature is expected to fluctuate between high 20s and low 30s, with a humidex of high 30s to low 40s.
The weather agency said while the extreme heat will affect everyone, it will pose greater risks to young children, pregnant women, older adults, people with chronic illnesses and those working outside.
"It is important to note that it is dangerous for at-risk populations," said Trudy Kidd, a meteorologist at Environment Canada. "We do tend to get heat warnings in the summer, and it is just at the point where people need to take special care."
Canada’s weather agency said it issues heat warnings when high temperatures pose an "elevated risk" of illnesses such as heat stroke or heat exhaustion.
Kidd said drinking water or other liquids and staying in cool places are “super important” during the heat wave.
Those who don’t have access to an air conditioner should seek out air-conditioned spots such as shopping centres, libraries, community centres or friends' and family's homes, she said.
“(If) mobility is an issue then another option could be taking cool showers or cool baths until you feel refreshed."
She cautioned Ontarians not to leave people or pets inside parked vehicles.
“If you are a healthy individual and you're used to the heat and this is no problem for you, it would be important to … visit your neighbours, friends and older family members that may have those chronic illnesses,” Kidd said.
Simon Legault, a meteorologist with Environment Canada in Quebec, said the same heat enveloping Ontario is also extending to southern Quebec.
“Most of the southern part of Quebec is impacted right now, from Outaouais to Laurentians to the Quebec City area, but that could extend to east and central Quebec in the next days,” Legault said.
“Those regions could be impacted into Friday and even Saturday for the eastern parts of the province because that’s when the cold front is moving in.”
Legault said even northern Quebec – notably in the Ungava Bay and Hudson Bay area – was experiencing intense heat on Tuesday comparable to temperatures in Montreal.
“We’ve seen 33 C or 34 C in the Hudson Bay area, so they are shattering some records there,” Legault said.
In Ontario, a spokesperson for Interfaith Coalition to Fight Homelessness, said the current heat wave impacts Toronto’s homeless population more than other groups in the city, calling it an “emergency situation.”
“It is just not a matter anymore of having cooling centres in the summer and warming centres in the winter,” Rafi Aaron said.
“In the last 10 days, when twice Toronto had the worst air quality in the world, people were told not to be outdoors. But if you're unhoused, you have to be outdoors.”
Environment Canada said people who live near Ontario's lakes may see some reprieve from the heat as temperatures in those areas tend to be cooler thanks to lake breezes.
"Lakes tend to take a while to warm up, whereas the land we live on can heat up quite quickly with the sun," Kidd said.
This report by The Canadian Press was first published July 4, 2023.
Sharif Hassan, The Canadian Press
