What to know
- Meteorologist Doug Gillham says the GTA’s recent heavy rain, hail and thunderstorms are being driven by a clash between hot, humid air to the southwest and cooler air pushing south, creating a “Ring of Fire” along the boundary.
- Rainfall has been highly uneven across southern Ontario, with some areas seeing devastating flooding while Toronto has largely missed the most intense storms, and Scugog was hit by baseball-sized hail on Aug. 8.
- Gillham says heat and humidity are providing fuel for the thunderstorms, while wildfire smoke drifting south is mainly causing haze and may lower temperatures slightly, but is not contributing to the heavy rain or stronger storms.
- He says there is no single explanation for the active storm pattern, noting a rapidly strengthening El Niño and the resulting stronger jet stream may be a bigger factor than climate change, which could also produce conditions that suppress thunderstorms through stronger heat domes.
With multiple days of heavy rain and severe thunderstorm warnings in Toronto, one weather expert says that opposing temperatures are clashing and causing the inclement conditions.
August has been an especially wet month for both Toronto and the rest of southern Ontario, with Environment Canada releasing multiple alerts due to extreme weather.
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In an email to Now Toronto, Doug Gillham, a meteorologist with The Weather Network, said the heavy rain, and even the hail, the Greater Toronto Area (GTA) has experienced in the past couple of weeks has been inconsistent in different towns across the province.
“Rain totals have been widely variable across the GTA and southern Ontario this summer, ranging from below normal to historically wet with devastating flooding, especially in the Niagara region and in [the] Ottawa area,” he explained.
“We have had more frequent than normal threats for thunderstorms, but some places have been consistently missed while most places have been hit more often than not.”
As of Wednesday, towns such as St. Catharines and Niagara Falls are experiencing flooding in thousands of homes due to extreme rainfall over multiple days, with homes filled with debris and sewage water due to the flood.
Alternatively, Toronto was mostly missed by the thunderstorms, with the rainfall that did dampen the area having little to no impact on the city.
A bit northeast of Toronto, the municipality of Scugog and the community of Port Perry saw the brunt of a hailstorm that began as a thunderstorm on Aug 8.
Hailstones the size of golf balls and baseballs rained down on the area, causing damage to vehicles and infrastructure outdoors in the area.
Gillham said the extreme weather is a phenomenon called the “Ring of Fire.”
“We are near the battleground between hot and humid conditions to the southwest of our region and cooler conditions to the north, which are pushing south into the region,” he stated. “The battleground around the edge of the hot and humid conditions is often referred to as the “Ring of Fire” since we tend to see frequent rounds of thunderstorms tracking along the boundary.”
Gillham added that the recent higher temperatures also play a factor.
“Heat and humidity are the fuel for thunderstorms, so that has been a key to the development and intensity of the thunderstorms,” he said. “…Often this summer southern Ontario has been near the battle zone between the very warm and humid air and cooler conditions attempting to push into our region, and that has been a major key to the very active pattern.”
Is the GTA susceptible to thunderstorms?
Gillham says that when it comes to the GTA being more prone to thunderstorms, the answer is “yes and no.”
While thunderstorms can often track along the boundaries between Lake Ontario’s cool temperatures and warmer conditions further from the lake, where intense amounts of rainfall tend to be more random.
“Sometimes it is close to the lakeshore and other times it is near or north of the 407,” he explained.
No broad trends affecting thunderstorms
With Toronto seeming to experience more heatwaves every summer, Gillham says that while higher temperatures could influence intense storms, heat domes could reduce that chance.
“…A warmer climate will also have stronger heat domes which suppress the development of thunderstorms due to the sinking air that is associated with these systems,” he said.
He explained that because of these conflicting facts, the answer to the question of whether climate change will provoke more thunderstorms does not have a simple answer.
“It is quite possible that in future summers, many will be asking if climate change is the reason for a drought during that particular summer,” he said.
Gillham concludes that the severe thunderstorms in southwestern Ontario can’t be attributed to one main trend.
He explained a stronger El Niño pattern can also be one of the reasons for more of these storms in the area.
“…The rapid transition to a strong El Niño pattern, which is giving us a more active and stronger jet stream and causing our region to be in the battleground between the heat and humidity and cooler weather,” he explained.
“The rapid transition to a strong El Niño pattern is likely more of a factor than just climate change.”
