Ontario Can Expect Little Relief From Heat and Humidity This Summer, Experts Say

A person relaxes in the shade by the Ottawa River during a heatwave in Ontario, on July 4, 2023. The Canadian Press/Sean Kilpatrick

The days-long heatwave hitting much of Ontario this week is the beginning of a very hot and humid summer, weather experts say.

Environment Canada and the Weather Network are predicting warmer than normal temperatures this summer for the entire province as well as for the central Prairies, Quebec, and Atlantic Canada.

While June will be a mixture of cool weather interspersed with above-normal temperatures, there will be little relief for the rest of the summer, says Weather Network senior meteorologist Doug Gillham.

In Ontario, the heat is “expected to build through July and August and linger into September,” Mr. Gillham said in a blog post, adding that the Greater Toronto area, the Ottawa region, and southwestern Ontario can expect high heat and humidity throughout the summer months.

The entire province can also look forward to “extended periods of dry weather,” especially across northern Ontario, with an increased risk of poor air quality from smog and smoke, he said.

Similar conditions are expected across much of central and Eastern Canada.

Extreme Heat Risks

Environment Canada has issued extreme heat warnings throughout most of the province this week as temperatures soar into the 40s. And with those warnings come the increased likelihood of heat-related illnesses like heat stroke and even death.

“The risk for heat-related illnesses will sharply increase during this… heat wave as a result of the expected duration of hot temperatures and high humidity,” Mr. Gillham said, adding that intense, humid heat is a “silent killer.”

“Extreme heat is a leading weather-related cause of death around the world, claiming more lives every year than tornadoes and hurricanes combined,” he said.

A heatwave in British Columbia led to the deaths of 619 people in 2021 and the deaths of 208 people in Quebec in 2010, according to Environment Canada statistics.

Staying inside out of the sun’s rays may seem like the perfect solution for staying safe, the agency said, but the majority of heat deaths in Canada occur indoors. Lack of air conditioning or other cooling methods can lead to dehydration and can exacerbate existing health conditions like asthma or heart disease.

Energy Issues

Francis Bradley, CEO of the industry association Electricity Canada, said the country’s electricity grid is becoming increasingly vulnerable to the rising severity and duration of extreme weather.

“We saw new peak demands hit last summer in Ontario, we saw new peak demand hit last winter in Quebec, for example,” Mr. Bradley said. “In most regions of the country, the extremes are increasing.”

All regions are facing rising demand for electricity, spurred in part by the increased demand for electric vehicles and other clean-energy innovations, and no single province has a perfect solution, he said.

“Ontario, for example, has had concerns and has asked customers to reduce consumption during heat waves in the past,” he said.

The summer—and all-time—peak for electricity demand in Ontario was set on Aug. 1, 2006, at 27,005 megawatts when the temperature reached a sweltering 36 degrees in Toronto, but felt like 47 degrees with the humidity.

The peak demand wasn’t expected to reach that level June 18, according to the Independent Electricity System Operator (IESO), despite temperatures reaching 39 degrees with the humidity. The Crown agency estimated peak demand at 23,617 megawatts by 7 p.m. and is predicting only slightly higher demand June 19.

Hydro One says one of the best ways to keep electricity use—and the grid—stable is to set the thermostat at a reasonable level during a heatwave. The utility company recommends setting the temperature at 25 degrees when family members are home and at 28 degrees when the house is empty.

“For every degree you dial up the temperature, you use about 3 to 5 percent less energy,” Hydro One said in a press release about how to conserve electricity.

Being Ready

With another hot summer in the forecast for Ontario, the province held Exercise Heatwave last month as part of Emergency Preparedness Week to help teach municipalities how to deal with extreme heat emergencies.

The province stressed having cooling centres designated within the community for those without air conditioning. Popular sites include shopping malls, libraries, and other public buildings. Many cities such as Toronto and Ottawa have interactive maps and resources to help those without air conditioning or housing to stay cool.

The province suggests setting up health checks for family members and friends who are at increased risk during extreme heat events, particularly if they do not have access to air conditioning.

Extreme heat can be especially dangerous for older adults, young children, pregnant women, people with chronic illnesses, people who work or exercise in the heat, as well as people with low incomes or experiencing homelessness, according to Health Canada.

“Heat illnesses can affect you quickly, and can lead to long-term health problems and even death,” the agency said in an advisory.

High body temperature, skin rash, muscle cramps, nausea or vomiting, heavy sweating, headache, rapid breathing and heartbeat, extreme thirst, and dark urine are all signs of heat exhaustion.

If confusion and lack of coordination, dizziness or fainting, and very hot, red skin with no sweating are also present, that is a sign of heat stroke, the agency said, adding that the condition should be treated immediately by a medical professional.

Health Canada recommends drinking plenty of water before feeling thirsty to decrease risk of dehydration.

The agency also recommends making meals that don’t need to be cooked in an oven, and blocking the sun by closing awnings, curtains, or blinds during the day to keep the house cool. Those with an air conditioner should turn it on before it gets hot while those with a window unit should focus on cooling only one room where the family can go for heat relief.

When outdoors, Health Canada suggests wearing loose-fitting, light-coloured clothing and a wide-brimmed hat made of breathable fabric. It is also important to wear sunscreen because sunburned skin “loses its sweating efficiency,” making it harder for the body to regulate its temperature.

The Canadian Press contributed to this report.