September 2023 is off to a hot, humid start in Ontario — but will it last?

The start of September was a scorcher for much of southern Ontario, but will the rest of the month see above-normal temperatures?

Global News’ chief meteorologist Anthony Farnell says after a “scorching start,” the weather is “about to return to more seasonal conditions in the coming days.”

The first week of September — particularly around the Labour Day long weekend — saw temperatures hovering around the 30 C mark, with humidex values soaring into the high 30s and, at times, into the 40s.

Labour Day on Monday was the hottest day on record so far this year at 34 C in Toronto, surpassing a very warm June 2 at 32 C, according to data from Environment Canada.

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Temperatures reached almost 32 C on Sunday, 33 C on Tuesday and 31 C on Wednesday in Toronto.

Warm temperatures persisted into Thursday which is forecast to see a high of 27 C but will feel more like 34 with the humidity, according to the weather agency.

According to Farnell, a heat dome had settled over the Great Lakes for several days, which brought the heat and humidity.

“That ridge is now breaking down and will be replaced with a much cooler trough through the middle of September,” he said.

“This means an increased change of showers along with highs in the upper teens and low 20s which is actually slightly below normal.”

According to Farnell, this trough will “also play an important role” in steering a major hurricane Lee in the Atlantic by either directing it out to sea or up towards the northeast U.S. and Atlantic Canada.

“For southern Ontario, we don’t have to worry about any tropical storms or hurricanes in this pattern,” Farnell explained.

Farnell said there “are signs” that above-seasonal temperatures could return in late September, and added that October could also be a “mild month” across the region.

“But gone are the heat warnings and 30-plus-degree temperatures,” Farnell said, “likely until next summer.”