Historic warmth building in Ontario with all-time highs, warm nights

Nature is grasping to hopes of summer as we head into the beginning of October this year, with a significant ridge building over Ontario threatening to topple all-time monthly heat records.

Moosonee’s predicted high on Wednesday could shatter the community’s warmest temperature ever recorded in October, which would be an astounding feat after it witnessed its hottest-ever September temperature just a few weeks ago.

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This flashback to summer in the heart of fall will build over Ontario courtesy of an atmospheric blocking pattern known as an Omega block.

Named for its resemblance to the Greek letter Omega, this kind of blocking pattern sees a ridge of high pressure bookended by troughs on either side, essentially locking the ridge in place for days on end.


A pattern like this during the true heart of summer would bring a terribly dangerous stretch of excessive heat, but the idea of "seasonable" changes quickly this time of year.

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Temperatures 10-15+ degrees above seasonal at the beginning of October just means short-sleeves instead of sweaters.

Warmest October Temps
Warmest October Temps

As a result of this stubborn pattern, we’re going to see a very long stretch of abnormally warm conditions bathe Ontario for most of the first week of October.

Record highs are likely to fall over the next couple of days, especially toward cottage country and northern Ontario. We’re likely to see the warmest start to October in over a century in places like Ottawa and Timmins.

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Moosonee could break its all-time October temperature record. It's current monthly record is a 27.7°C reading back in October 2011. The community’s predicted high on Oct. 4 is 28°C.

It’s not just daytime highs that’ll come in warmer than usual. Warm days will bleed into warm nights, especially across southern Ontario, where some spots are on the lookout for their warmest minimum temperatures ever recorded during the month of October.


Toronto’s low temperature on Wednesday could bottom-out at an even 20 degrees, which would become the city’s warmest October low, beating a 19.4°C morning recorded back in October 2002.

Some sense of normalcy will eventually return, of course, and the warmth is on borrowed time. We’re likely to see a major pattern flip toward more seasonable conditions by the end of the week or next weekend.

Find out what the rest of October has to offer in our October outlook.

Thumbnail courtesy of Getty Images.

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