'Sweltering humidity:' Ontario welcomes summer with storm risk, and a heat wave
Thunderstorms and rain will impact southern Ontario this weekend before a potent heat wave rolls in for the start of summer
In a double switch-up of the phrase "the calm before the storm," Ontario is set for thunderstorms ahead of an early summer heat wave coming Sunday.
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Rounds of thunderstorms are forecast for southern Ontario starting Friday, and continuing through Saturday. Starting Sunday, a heat wave will move in from the central U.S., ushering in several days of elevated heat and humidity.
Be sure to keep an eye on local weather alerts as conditions change.
Friday and Saturday: Storm threat ahead of the heat
Going into the late afternoon hours on Friday, a long boundary will drape itself over southwestern Ontario, bringing scattered showers and thunderstorms.
This will extend into the evening hours for parts of the Greater Toronto Area (GTA), towards the Huron shores and into the southwest.
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Between Windsor and London is where you’ll see more severe weather, with isolated severe thunderstorms bringing torrential rain and strong winds to the area.
From Windsor to Ajax, we’ll see high amounts of moisture in the atmosphere, creating significant downpours across the forecast thunderstorm area, as well.
On Saturday, a high-pressure ridge responsible for the extreme heat will nudge its way closer to Ontario.
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What is known as the ‘ring of fire,’ where thunderstorms and rain track along the outer edge of a high-pressure ridge, will continue to bring rounds of large clusters of thunderstorms from Friday night and through Saturday.
These storms will sweep rain across southern Ontario, yet it’s uncertain what time they will land on Saturday.
After the storm, we’ll start to see the heat and humidity start to build over the next several days, starting Sunday.
Ontario’s early summer heat wave
On Sunday, southern Ontario will see temperatures climb to the low to mid-30s with humidex values towards the mid-40s.
From the end of the weekend going into Tuesday, the three-day stretch will focus on the extreme heat and humidity, with temperatures at 33°C or higher forecast for the GTA and into the southwest, where humidex values during the daytime will be in the mid 40s.
This time last year southern Ontario was also going through a heat event where humidex values climbed into the mid 40s.
Tuesday will see temperatures come down slightly from their Monday highs for most of the province.
Areas like Niagara Falls and London won’t change in real terms, while Kingston and Windsor will see an increase in the heat.
Taking safety precautions during this heat wave will be important for the vulnerable population.
Overnight lows will remain in the mid 20s so little relief is expected through the overnight hours.
Will this heat be record breaking?
If Toronto's airport reaches a temperature of 35°C, which is 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 Toronto Pearson, it will have been 13 years 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. Staying well hydrated and limiting outdoor activity, taking lots of breaks and cooling off when needed will be important.
Below are some tips to keep yourself safe going into the heat event next week.
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.
