Toronto is set to bask in a stretch of late-summer warmth this week, with forecasters calling for sunny skies and steadily climbing temperatures that will push well above the seasonal norm.
Environment Canada’s outlook shows daytime highs near 24 °C on Monday and Tuesday, rising to 26 °C on Wednesday and peaking at 28 °C on Thursday under mostly clear skies. Overnight lows are expected to remain mild, hovering in the mid-teens, offering little of the crispness that often signals the approach of autumn.
Though subject to change, temperatures are currently forecast to drop by the end of the week and the weekend with additional cloud cover, but no upcoming rain or showers as of yet. Friday’s nighttime low could see temperatures fall to 9 °C in the city.
Historically, mid-to-late September in Toronto is cooler, though not as low as one would expect. Climate records from the past two decades indicate that average daytime highs between Sept. 15 and Sept. 22 sit around 22 °C, with lows near 14 °C. While warm spells are not unheard of, sustained highs in the upper 20s this late in the month are relatively rare.
“This is not too unusual for Toronto this time of year,” says 680 NewsRadio meteorologist Carl Lam. “We typically get a few pushes of warmer air during the month of September, so while it may feel odd, it may also be a recency bias since it’s been so cool since September started.”
Forecast highs could deliver one of Toronto’s warmest mid-September weeks in years
In 2023, the same week saw highs ranging from 19 °C to 23 °C, with several days of rain. Even in 2024, when September began on a warm note, temperatures during this period topped out at 25 °C only once. This week’s forecast, if it holds, would mark one of Toronto’s warmest mid-September stretches in recent memory.
If Thursday’s forecast high of 28 °C is reached, it would come within a few degrees of the record for Sept. 18 in Toronto, set at 31.1 °C in 1942.
“The warmest conditions are expected during the middle of the week, with temperatures climbing back into the upper 20s, and the humidex values could be close to 30,” Lam says. “It’s a bit of a callback to summer, but some cooler temperatures are on the way for the weekend.”
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