Environment Canada has issued a yellow heat warning for parts of the Golden Horseshoe, including the City of Hamilton and the Niagara Region, as a surge of warm, humid air settles over southern Ontario.
What to expect this week
The federal agency says the heat event is likely to persist through Wednesday and may continue into Thursday. Temperatures in the warned area are forecast to climb above 30 C for the next several days. Although Toronto itself is not under the formal warning, humid conditions have returned to the city and the broader Greater Toronto Area.
"The ‘heat event’ is expected to last through Wednesday, possibly into Thursday."
Wednesday in Toronto is expected to be mainly cloudy with a significant chance of showers. Environment Canada puts the morning chance of precipitation at about 70 per cent, with showers or thunderstorms possible late in the afternoon. The forecast daytime high is around 29 C, with a humidex making it feel closer to 37.
Wet, unsettled conditions are likely to continue on Thursday, when the daytime high will fall to about 26 C. The agency then projects a shift to drier weather for the upcoming long weekend, with daytime temperatures easing into the mid-20s and predominantly sunny skies.
Short-term forecast snapshot
| Day | Toronto forecast |
|---|---|
| Wednesday | Mostly cloudy, showers possible; high ~ 29 C (humidex ~ 37) |
| Thursday | Showers continuing; high ~ 26 C |
| Friday | Sunny; high ~ 26 C |
| Saturday | Sunny; high ~ 25 C |
| Sunday | Sunny; high ~ 24 C |
Environment Canada highlights that while Toronto will see relief from the most extreme conditions over the long weekend, the Golden Horseshoe areas under the yellow warning should prepare for sustained heat and humidity through midweek.
Health and safety considerations
Heat warnings are issued to alert residents to conditions that can increase the risk of heat-related illness. When temperatures and humidity rise together, the body’s ability to cool itself is reduced. People most at risk include older adults, infants and young children, those with chronic medical conditions, and anyone working or exercising outdoors.
Simple precautions can reduce risk and help people stay safe during a heat event:
- Stay hydrated — drink water regularly even if you do not feel thirsty.
- Seek cool or air-conditioned spaces during the hottest part of the day.
- Limit strenuous outdoor activity when possible; take frequent breaks if working outside.
- Check on vulnerable neighbours, family members and friends.
- Watch for signs of heat-related illness: dizziness, weakness, confusion, rapid heartbeat or hot, dry skin.
Local authorities and public health units typically provide cooling centre information and additional guidance when warnings are in effect; residents in affected communities should monitor municipal bulletins and Environment Canada updates.
For those planning travel or outdoor activities in the Toronto area, expect a muggy start to the week, a wet middle period with the chance of thunderstorms, and a marked improvement by the long weekend with sunnier, milder conditions and a lower chance of rain.
We will continue to watch Environment Canada advisories and will update forecasts as conditions evolve.
