A formidable ridge of high pressure building over the Great Lakes has prompted a spell of unseasonable temperatures to build over most of Ontario, giving folks an extended taste of summer.
The result has been daytime high temperatures coming in five to 15 degrees above seasonal, or higher, for many communities. While that is an unusual burst of comfortable warmth for this late in the season, it’s not unprecedented.
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What’s noteworthy about the warmth was Toronto’s low Monday morning was actually warmer than the normal daytime high for this time of the year.
However, that will soon go away as fall returns to the picture this week, and in an abrupt fashion, too. A strong cold front will track across the region on Wednesday afternoon and evening, sending temperatures back down to more reflective values of the season.
Warmth will soon be replaced with familiar fall temperatures
Ridges foster sinking air, which warms up and dries out as it descends toward the ground. The end result is usually sunny skies, above-seasonal temperatures, and a noticeable lack of rainfall.
The ridge’s influence peaked on Monday with the event’s warmest temperatures. Daytime highs in the mid-20s were seen throughout southern Ontario.
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Warm air will even spread toward Moosonee by Tuesday, where we could see a high pushing 20 degrees.
It’s worth watching the potential for poor air quality in some communities as this stagnant pattern also helps trap pollution closer to the ground. Some degradation in air quality is expected to persist over the next few days.
We’re in the middle of fall, after all, and all good things have to come to an end. A cold front pushing into Ontario on Wednesday afternoon and evening will serve as our return to reality. Temperatures will even fall a few degrees below seasonal for some areas by Thursday.
Scattered showers are expected with the cold front, but rain amounts are not expected to be substantial and some places will miss out.
Partly sunny and much cooler temperatures are expected on Thursday. Saturday will be blustery and chilly with scattered showers and possibly lake-effect showers. Sunday will be fair and cool.
A few days of much warmer weather are expected to arrive next week, but temperatures will approach and could even exceed 20 degrees again during the middle of next week. However, this stretch of milder weather could become more unsettled, as well later next week.
Unusual, but not unprecedented
How unusual is this kind of warmth this late in the season?
It’s rare, but not unprecedented. Just about everyone in Ontario has seen a day reach at least 20°C well into November.
A memorable event unfolded in November 2020 when Pearson International Airport recorded a high temperature of 24.3°C, its latest 24-degree day on record. Hamilton saw a reading of 25°C that day.
Pearson airport’s latest 20°C day was Dec. 3, 1982, a day that saw Hamilton hit 21.2°C, as well.
Folks down in typically toasty Windsor take the cake, though, where we hit the 20-degree mark as late as Dec. 6 one year.
Stay tuned to The Weather Network for all the latest on conditions across Ontario.