After two weeks of temperatures above 25C every day, Toronto, the most populous city in Canada and the provincial capital of Ontario, has cooled down to below average temperatures. Last weekend was positively blistering, both days above 33C and the Toronto Public Health authority issued its only 'extreme heat alert' this year.

The average September temperature in Toronto is 21C, but in this humid continental climate, the highest recorded since 1840 has been 37.8C. That was missed by a few degrees, but 33.6C, as felt on Sunday, seems to be the hottest September day in 126 years.

Toronto has not been alone – all of eastern Canada has enjoyed this delay to the change of season. According to Environment Canada, temperatures in the nation's capital, Ottawa, reached 33C on Monday afternoon, breaking the record for the hottest September 25 ever recorded at Ottawa International Airport.

The eastern side of the US has had similar weather largesse: from the Midwest to the northeastern United States, the first week of 'the fall' has not only produced higher temperatures than those seen during summer but, according to the National Weather Service, "there has never been a heat wave of this duration and magnitude this late in the season in Chicago."

More than a dozen daily record highs were set on Wednesday in this part of the US. The weather stats at Weather Underground state that Ohio, Pennsylvania, New York, Vermont, New Hampshire and Massachusetts were all caught up in this unseasonal warmth. Saturday's high of 35C in Chicago marks the latest day in recorded history that the mercury has reached that level.

The ridge of high pressure responsible for the high temperatures has just collapsed and, as of Thursday, temperatures have all returned to, or dropped below normal. The cold front responsible also brought a little rain with it, coincidentally ending the driest run of days, at any time of the year, in Ottawa since 2009.