100+ mm in 3 hours: Heavy rain batters parts of southern Ontario
Southern Ontario experiences its wettest weather in over two months as a low pressure system draws in subtropical moisture, increasing rainfall totals in thunderstorms through Thursday
Southern Ontario is set to experience another round of torrential downpours through Thursday, following localized flooding that impacted parts of the Greater Toronto Area (GTA) on Tuesday evening.
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Rain from the system began spreading across the region during the early hours of Wednesday, as well. A series of more intense, moisture-rich thunderstorms tracked along the northwestern shoreline of Lake Erie, delivering continuous torrential rainfall and pushing precipitation totals to significant levels.
By midday Wednesday, radar indicated rainfall totals between 100-200 mm in a localized area of extreme southwestern Ontario. Residents are urged to stay alert to the changing conditions, especially with an elevated risk of significant flooding.
System draws in subtropical moisture through Thursday, more heavy rain totals for southern Ontario
The unorganized low, moving south of the Great Lakes, is set to bring additional widespread showers and scattered thunderstorms.
The system will pull in subtropical moisture, increasing rainfall totals in areas affected by thunderstorms. While showers will remain scattered across the region, isolated thunderstorms could deliver over 50 mm of localized rain, potentially causing additional pooling and ponding.
It is important to remain weather-aware, and stay up-to-date on all of the latest watches and warnings.
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As the system continues to move east, scattered showers and thunderstorms are expected in eastern Ontario on Thursday. The GTA and southwestern Ontario may see a few isolated showers or thunderstorms trailing behind the low pressure system.
High pressure is set to move in afterward, establishing another dry weather pattern in its wake.
Wettest weather in more than two months
Toronto Pearson Airport (YYZ) recorded 38.1 mm of rainfall on Tuesday as slow-moving thunderstorms rolled through the region. This marked the city’s wettest day in over two months, since July 20, which saw 48.1 mm.
Dry conditions have dominated the region, with much of southern Ontario receiving less than half the normal rainfall from late August through most of September, leading to widespread drought concerns.
However, the last three days (Sept. 21–23) brought significant rainfall to Toronto. A total of 73 mm was recorded at Pearson—pushing the city to its average September rainfall totals in just three days.
A pleasant first weekend of Fall
Saturday will bring mostly sunny skies and warm temperatures, ranging from the low to mid-20s, accompanied by gusty winds. Clouds will increase into the afternoon, bringing a chance of passing showers later in the day, mainly in areas near cottage country.
Sunday is expected to be mostly sunny and slightly cooler, with temperatures a few degrees above seasonal norms, despite the drop.
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Looking ahead into next week, warmer-than-normal temperatures are expected to persist. A drier pattern is forecast to take hold, with abundant sunshine anticipated through at least midweek.
Stay with The Weather Network for all the latest on conditions across Ontario.