Canada’s national weather agency is warning of a "prolonged heat event" starting Monday that is expected to bring “dangerously hot and humid conditions” to much of southwestern Ontario.

Late Sunday afternoon, Environment and Climate Change Canada (ECCC) issued a heat warning for a large swath of Southern Ontario, including London, Toronto, Niagara, Owen Sound, and Kingston, Ont.

According to Environment Canada, daytime highs in the area are expected to soar into the mid-thirties, with humidex values of 40 to 45 degrees Celsius, through much of the week.

“There will be little relief overnight as lows are expected to be 20 to 23 C with humidex values of 26 to 30," the warning reads.

In Toronto, thunderstorms are also in the forecast for Sunday night into Monday.

Environment Canada issues a heat warning when two or more consecutive days are forecasted with daytime maximum temperatures of 31 degrees Celsius or higher, along with a minimum nighttime temperature of 20 degrees Celsius or higher, or when two or more consecutive days are forecasted with humidex values reaching 40 or higher.

“Due to climate change, Toronto is expected to experience higher summer temperatures, unpredictable weather and more extremely hot days,” the city said.

The latest weather updates can be found on ECCC’s website

Toronto heat



The high temperatures will pose a risk of heat stroke, along with deteriorating air conditions, ECCC said in its warning.

The national weather agency is advising older adults, infants, young children, pregnant people, and those with disabilities to take extra care to mitigate the risks and watch for signs of heat illness. These include swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions.

If you believe you or someone you know has a high body temperature, has stopped sweating and/or becomes confused or unconscious, ECCC advises calling 911.

While waiting for help, the agency says to move the person to a cool place, apply a cool compress to large areas of their skin, and fan the person as much as possible.



From May 15 to Sept. 30, the City of Toronto is activating its annual Heat Relief Strategy. A key part of this strategy is the opening of Cool Spaces like libraries, community centres and pools so that residents can seek relief from the heat.

On Saturday, Toronto’s 10 wading pools and 10 outdoor pools opened ahead of schedule to “provide residents with more options for staying cool during hot weather,” the city said in a news release.

For more information, including pool hours, visit the city’s Swimming & Water Play web page.

Tips for residents to stay safe during the upcoming heat wave:

- Stay hydrated. Drink water regularly, even when not thirsty.

- Plan outdoor activities for cooler times of the day.

- Seek shade or use an umbrella to avoid direct sun exposure.

- Use a fan to circulate cool air indoors when the temperature is below 35 degrees Celsius.

- Keep blinds or curtains closed during the day to block out the sun.

- Wear lightweight, loose-fitting clothing and wide-brimmed hats outdoors.

- Take cool showers or use cool, wet towels to cool down.

- In an emergency, always call 911.

(Courtesy City of Toronto)

More information and tips for preventing heat-related illness can also be found on the city's Keep Cool webpage