Dangerously hot weather about to spread back into Ontario again
The end of this week features the return of some dangerous heat and humidity across southern Ontario. Heat warnings are in effect
Ontario is bracing for the return of intense heat and humidity after a brief break earlier this week.
DON'T MISS: U.S heat will soon spill into Eastern Canada, bringing back 30 C weather
On Thursday, Toronto’s high is forecast to reach 34°C, with a humidex of 43, making conditions particularly uncomfortable. Across southern and central Ontario, humidex values are expected to range from the low- to mid-40s.
Heat warnings have already been issued.
What’s driving this heat surge? The southwesterly flow around a high pressure centred over the southeastern United States. Some of the associated heat is spilling into Canada, particularly Ontario and Quebec, along the northern edge of the pressure ridge.
The last few days of July will feature this heat event shifting toward the western U.S., as the high heat spills back into Western Canada, as well.
Residents are urged to monitor heat alerts and take precautions to stay cool and hydrated.
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This summer has seen a lot of scorching heat across the GTA
The summer of 2025 has been notably hot across southern Ontario and the Greater Toronto Area (GTA). As of July 22, Toronto Pearson International Airport (YYZ) has recorded 14 days with temperatures reaching 30°C or higher.
Breaking it down, there were five such days in June, and nine so far in July. The highest temperature recorded this summer was 36°C on June 23, during a heat wave that spanned June 22–24. Over that period, daytime highs exceeded 34°C, and overnight lows stayed above 20°C.
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Another stretch of significant heat occurred from July 11–16, with five consecutive days hitting 30°C or higher.
While this summer has been hot, it hasn’t yet surpassed the July all-time high of 37.9°C, recorded on July 7, 2011, according to Environment and Climate Change Canada (ECCC).
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Hot weather safety tips
Drink plenty of water. Avoid caffeine and alcohol, which can be dehydrating.
Avoid direct sunlight, especially during peak hours and when the UV rating is high.
Wear lightweight, loose-fitting clothing.
Use air conditioning when possible. If you do not have access to air conditioning, consider visiting a cooling centre, a shopping centre, or a public library.
Check on elderly relatives and other vulnerable neighbours.
