Ontario's last 20°C days are numbered—but not gone yet
Warmth will likely last a bit longer in southern Ontario, but forecasts predict it will be the region's last taste of 20-degree weather this year.
Southern Ontario isn't ready to give up the keys to winter just yet.
Forecasters predict that Tuesday will comfortably exceed 20°C across much of the region, a nice bonus for mid-October — before a fast drop midweek and another warm-up over the weekend.
Historically, that is when T-shirt weather typically ends. Over the last decade, Toronto's final 20°C day has averaged October 22, with the most recent record set on November 10, 2020.
Ottawa follows a similar seasonal pattern, with its latest 20°C temperature falling between October 10 and November 11.
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Few misses, quick flips
While most Octobers provide at least one warm encore, a handful have completely missed the mark entirely.
According to Toronto's weather records, the only years when the city never surpassed 20°C were 1977, 1981 and 2009.
The earliest "final" warm day occurred on September 17, 1977, when the temperature reached 23.5°C—and that was it.
Even a mild fall can change quickly. Fall 2020 was one of the warmest in recent memory, but snow fell quickly weeks later: Ottawa received 10.4 cm on November 25, Toronto received 19.4 cm by November 22 and Windsor received 8 cm on November 30th.
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When warmth overstays its welcome
In December, temperatures can reach 20°C, which is unusual but not impossible.
Historical outliers include December 31, 1875 in Windsor (20.0°C), December 14, 2015 in Welland (20.1°C) and a pair of readings on December 3, 1982, when both Toronto (20.0°C) and Hamilton (21.2°C) made it feel like fall would never end.
However, this year's warmth is unlikely to last very long. With milder-than-normal weather expected to last until late October, a few more 20°C days are inevitable before a pair of cold fronts eventually close the door until spring.
So, grab your light jacket while you can, Ontario's extra stretch of warmth will not last forever.