Southern Ontario Is Under Another Heat Warning: Environment Canada

People enjoy the view of the CN Tower and the Toronto skyline from the Toronto Islands on Lake Ontario, on Sept. 14, 2023. Valerie Macon/AFP via Getty Images

Environment Canada has issued another heat warning for part of southern Ontario as temperatures are expected to rise to 35 degrees.

The heat event is expected to begin on July 24, with daytime highs reaching 35 degrees and humidex values making it feel like 44 degrees, according to a July 23 alert issued by Environment Canada.

The alert is for a section of southern Ontario that borders Lake Ontario and spans from St. Catharines to Toronto, including Haldimand County, Brantford, Milton, Brampton, Richmond Hill, and Markham.

Residents may experience little relief from the heat as nighttime lows are only expected to drop to 20 to 23 degrees, the agency says.

Environment Canada expects the heat event to last into July 25, although temperatures are not expected to be as high as the first day of the event.

Daytime temperatures could reach 30 degrees, while humidex values are expected to make it feel like up to 40 degrees. Nighttime temperatures should drop to a low of 21 degrees, again “providing little relief from the heat,” the alert says.

While the federal agency expects the hottest conditions on July 24, it says the heat event could continue through the weekend for some areas.

Heat Safety

“Take action to protect yourself and others – extreme heat can affect everyone’s health,” Environment Canada says.

The agency suggests drinking water often and before feeling thirsty to adequately replace fluids and prevent dehydration. It also recommends closing blinds or shades, opening windows if the outside temperature is cooler than inside, turning on air conditioning, using fans, or moving to a cooler area inside.

Those who are unable to find relief from the heat in their living space are advised to move to a cool public space, such as a cooling centre, community centre, library, or shaded park.

When possible, plan outdoor activities for the coolest parts of the day, limit direct sun and heat exposure, and wear lightweight, light-coloured, loose-fitting clothing, and a wide-brimmed hat, the agency advises.

Symptoms of heat exhaustion can include headache, nausea, dizziness, thirst, dark urine, and intense fatigue. The agency says to stop activity and drink water when noticing signs of heat exhaustion.

Heat stroke is a medical emergency, the agency warns. Symptoms of heat stroke include red and hot skin, dizziness, nausea, confusion, and change in consciousness. Environment Canada advises those who experience these symptoms to seek emergency medical care.

Health Canada says health risks are greatest for older adults, infants and young children, people with chronic illnesses, low-income individuals, those experiencing homelessness, and people who work or exercise in the heat or are unable to keep their living spaces cool.