It’s going to be a hot start to the week as with the first official “heat event” of the season is set to come to the Greater Toronto and Hamilton Area on Monday afternoon.
According to Environment Canada, there will be daytime highs near 30 C, with humidex values near 36. Overnight lows are expected to hover around 18 to 20 C, the national weather agency said.
The heat event is expected to last until Tuesday night.
On Sunday afternoon, Environment Canada issued a yellow warning for heat for Toronto, Burlington – Oakville, Caledon, Hamilton, Halton Hills – Milton, Mississauga – Brampton, Niagara Falls – Welland – Southern Niagara Region, Newmarket – Georgina – Northern York Region, St. Catharines – Grimsby – Northern Niagara Region, and Vaughan – Richmond Hill – Markham.
Yellow warning – heat GTHA May 17 A yellow warning for heat was issued for several parts of the GTHA on May 17. (Environment Canada map screengrab)
The national weather agency is advising people to protect themselves and others as the extreme heat can “affect everyone’s health.”
“Determine if you or others around you are at greater risk of heat illness. Check on older adults, those living alone and other at-risk people in-person or on the phone multiple times a day,” Environment Canada said.
“Watch for the early signs of heat exhaustion in yourself and others.”
Those signs may include headache, nausea, dizziness, thirst, dark urine, and intense fatigue.
Anyone who experiences these symptoms should stop what they’re doing and drink water.
People enjoy the weather by the waterfront on a hot day at Sugar Beach park in Toronto, on Sunday, May 17, 2026. THE CANADIAN PRESS/Sammy Kogan People enjoy the weather by the waterfront on a hot day at Sugar Beach park in Toronto, on Sunday, May 17, 2026. THE CANADIAN PRESS/Sammy Kogan
Environment Canada further underlined that heat stroke is possible in this hot weather and should be considered a medical emergency.
“Call 9-1-1 or your emergency health provider if you, or someone around you, is showing signs of heat stroke, which can include red and hot skin, dizziness, nausea, confusion and change in consciousness,” the agency said.
Environment Canada said those waiting for medical attention due to possible heat stroke should cool the affected person by moving them to a cool place, remove extra clothing, and apply cold water or ice packs around the body.
Further people are being urged to drink water often and before you feel thirsty to replace fluids, close blinds or shades and open windows if outside is cooler than inside, and turn on air conditioning, use a fan, or move to a cooler area of your living space.
Humber Bay A cyclist enjoy the outdoors on a hot day riding across the Humber Bay Bridge in Toronto on Thursday, June 23, 2022. THE CANADIAN PRESS/Nathan Denette
The agency is advising anyone whose living space is hot should move to a cool public space like a cooling centre, a community centre, a library, or a shaded park.
People are also being advised to follow the advice of their region’s public health authority, plan and schedule outdoor activities during the coolest parts of the day, limit direct exposure to the sun and heat, and wear lightweight, light-coloured, loose-fitting clothing and a wide-brimmed hat.
“Never leave people, especially children, or pets inside a parked vehicle. Check the vehicle before locking to make sure no one is left behind,” Environment Canada noted.
More information about how to protect yourself from the effects of the extreme heat can be found online.
