Ontario temperatures soar as its second heat event of the summer arrives
The second heat event of the summer for Ontario begins this week, with temperatures soaring into the 30s and humidex values returning to the 40s
Ontario will see its second heat event of the summer as temperatures and humidex values will take a considerable jump this week.
Temperatures will climb well into the 30s during the peak of the event this week, with humidex values easily reaching into the 40s.
DON’T MISS: Why extreme heat is one of the world’s deadliest weather disasters
Even a relatively healthy individual can succumb to heat-related illnesses without proper precautions.
What could compound the heat issues will be the wildfire smoke that has reached parts of the province from Quebec, lowering air quality into this week.
Second heat event of the summer arrives
On Sunday, temperatures are feeling like the low 40s across northwestern Ontario as the heat and humidity ramps up. Areas such as Fort Frances, Dryden, Kenora will be affected. Southern areas will still see relatively comfortable temperatures, but under a blanket of haze from wildfire smoke.
Sunday night will be shockingly warm in northwestern Ontario, with an overnight low of 24°C or 25°C forecast for Dryden, Kenora, and Fort Frances. Thunder Bay has a Monday overnight low temperature forecast of 25°C, extremely warm for the city.
On Monday, Thunder Bay has a forecast high of 39°C, feeling like 44 with the humidex.
Those temperatures are the warmest so far in 2026 across northern Ontario, with many communities exceeding 35°C over the coming days.
On Monday, southern Ontario feels like the mid-30s once again, but now all of northern Ontario is feeling like the low 40s, with high moisture content in the atmosphere.
On Tuesday, the humidex values will rise even more.
Forecast humidex
Toronto: 44
London: 43
Windsor: 43
Kingston: 38
Ottawa: 44
Parry Sound: 40
WATCH: How to keep your cool as a parent this summer
Heat safety is vital
Extreme heat claims more lives around the world than any other type of severe weather.
Everyone is susceptible to heat-related illnesses without taking proper precautions, such as frequent breaks, adequate hydration, and air conditioning.
The compounding stress of hot days followed by muggy nights can be especially hard on vulnerable populations like the elderly, those with chronic health conditions, and folks who live without access to air conditioning. Keep in mind that certain medications can lower your body’s heat tolerance.