Heat, humidity set to intensify in southern Ontario as ridge settles in
A heat event will ramp up over a good portion of Ontario on Sunday, with soaring temperatures and humidity settling in for a few days this week. Take action to protect yourself and others as extreme heat can affect everyone’s health
Southern Ontario will endure a multi-day stretch of extreme heat and humidity beginning Sunday, with temperatures climbing into the low- to mid-30s and humidex values rising toward the mid-40s.
In fact, heat alerts stretch from Denver, Colo., and New Orleans, La., to Ottawa, Ont., as hazardous heat and humidity lock into place heading into the final full week of June. Heat warnings were recently expanded to include parts of northern and eastern Ontario.
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The thunderstorm risk will move north and east on Sunday, thanks to a heat ridge in place, but a greater chance will return to southern Ontario on Tuesday. However, there is still some uncertainty on the track of the cold front on Tuesday and the storm threat.
Storm risk shifts north and east on Sunday
A powerful ridge of high pressure developing over the eastern United States will nudge into Ontario through the end of the weekend.
The outer periphery of these heat ridges serve as the ideal environment for the development of thunderstorms, which then ride around the edge of the ridge like trains on railroad tracks.
A renewed round of thunderstorms will develop through the day Sunday, with the risk stretching from Winnipeg, Man., to western Quebec, with Kenora, Timmins, and North Bay, Ont., included.
The focus of the severe weather will be in southern Manitoba and northwestern Ontario, though, where strong wind gusts, large hail, heavy rain, and even some rotating storms are possible.
The active weather remains along the ridge, so not much rain is in the forecast for southern Ontario as we head into Monday.
We are tracking a cold front that is expected to sweep through on Tuesday, but there is uncertainty on how far south it will track to bring a little relief from the heat. However, folks should brace for active weather returning.
WATCH: How long will the heat in southern Ontario stick around?
Heat warnings in effect as temperatures soar
We’ll see temperatures and humidity increase to dangerous levels as the ridge of high pressure intensifies through Sunday and into this week.
On Sunday, the UV index is expected to be high, with levels reaching between 8-10. Make sure to wear sunscreen and limit sun exposure.
Sunday through Tuesday will serve as the focus of the extreme heat and humidity. We’re expecting at least three days of temperatures of 33°C or higher across most of the GTA and southwest—with daytime humidex values into the mid-40s.
Overnight lows will remain in the mid-20s, providing little relief for those living without reliable access to air conditioning.
If Toronto airport reaches a temperature of 35°C, likely on Monday, it would fall in the top-10 warmest June days on record.
If we see three or more consecutive days of 33°C or higher at Pearson airport, it will have been 13 years (since 2012) since we experienced a stretch of heat like this in June.
Record-breaking or not, this is an impressive heat wave that needs to be taken seriously.
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 neighbors.
Avoid strenuous activities during the hottest parts of the day.
If you experience symptoms of heat-related illnesses like dizziness, nausea, or confusion, seek medical attention.
Stay with The Weather Network for all the latest on conditions across Ontario.