Intense heat backs off a bit in Ontario but temperatures remain high
Record heat in Ontario gets pushed away on Wednesday, but prepare for the wildfire smoke.
Ontario has experienced its second significant heat event of the summer, shattering long-standing temperature records. Monday marked a historically hot day, with Armstrong, Ont., recording a temperature of 40.7°C. That sets a new all-time high for the community, highlighting the dangerous intensity of this heat event.
Toronto had to chance to set a new record on Tuesday, but it fell short of reaching or surpassing the previous high temperature.
The good news is that a cold front moved into southern Ontario late Tuesday, bringing Wednesday's temperatures back down toward the 30-degree mark with humidex values staying in the low-to-mid 30s.
RELATED: Dense wildfire smoke set to impact Ontario by Wednesday
Even a relatively healthy individual can succumb to heat-related illnesses without proper precautions.
Wednesday sees the heat relax a tad
A cold front pushed the extreme heat south, leaving still hot but generally drier weather in the short range for southern Ontario. By the weekend, temperatures should come down to the 20s again--in the seasonal range.
Expect smoky skies poor air quality on Wednesday and early Thursday in the Greater Toronto Area (GTA) as the wildfire smoke from northwestern Ontario pushes in. That could limit daytime heating by blocking part of the solar radiation.
Southwestern Ontario will be last to get rid of the mugginess, with lingering humidex in the mid-40s on Wednesday afternoon for Windsor and London. By Sunday, those cities will fall back to the 20s, with a humidex in the low 30s.
By early next week, a trough will develop on the eastern side of the country, keeping Ontario away from heat warnings. The pattern is set to push that heat back west where a ridge could redevelop heading into the later part of July.
Toronto fell short of new heat record
On Tuesday, Toronto fell short of its all-time record (38.3°C), but still saw its hottest day in 15 years.
Tuesday highs across various stations:
Pearson airport: 36.8°C (hottest since 2012)
University of Toronto (U of T)/Queen’s Park: 37.6°C (hottest since 2011)
Billy Bishop Toronto City Airport: 35.6°C (hottest since 2012)
The humidex reached 45 at Pearson and U of T.
Since weather records began at Pearson airport in 1937, the temperature has exceeded 37°C only six times before. The airport has topped 38°C just once, reaching its all-time record of 38.3°C on Aug. 25, 1948.
Muggy conditions will create uncomfortable outdoor environments, and those at risk for heat-related illnesses should limit time outside and stay hydrated.
Hottest temperatures felt in 90 years in northwestern Ontario
On Sunday, temperatures felt like the low 40s across northwestern Ontario as the heat and humidity continued to ramp up. More than 20 weather stations across the province recorded daytime temperatures above the 30-degree mark.
In fact, Sioux Lookout, located north of Dryden, briefly held Canada's record for highest daytime temperature so far in 2026 on Sunday after reaching 38°C. That title was quickly stolen, however, by Armstrong, northwest of Lake Nipigon, after temperatures reached the blistering high of 40.7°C on Monday afternoon.
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That is the hottest temperature recorded in Ontario since the 1936 heat wave, in the famous Dust Bowl era 90 years ago.
The 1936 heat wave did see even hotter temperatures, though that Armstrong couldn't quite reach. On July 11–12, 1936, Atikokan recorded a daytime high of 42.2°C. About an hour west, Fort Frances followed with the same reading the very next day on July 13, 1936.
Thunder Bay also set its own city record on Monday after reaching a daytime high of 39.5°C, becoming the hottest July day of all-time. The previous record was set on July 30, 1975, when temperatures reached 37.2°C. It is, however, not the hottest temperature ever recorded in the city. That record was set back on Aug. 7, 1983 when temperatures reached 40.3°C.
WATCH: Heavy wildfire smoke to blanket southern Ontario
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.