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Ontario: Fall-like temperatures continue Sunday, but summer isn't over, yet

Saturday, September 7th 2019, 8:00 pm - Cool start to September, but temperatures could surge in the south by mid-week.

EDITOR'S NOTE: This story is no longer being updated. Please click here for the latest forecast.

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Despite the sooner-than-expected fall-like temperatures in Ontario, summer isn't ready to give up just yet. By mid-week warmth could surge back into southern areas of the province, particularly the southwest, where there is the possibility of humidity returning, however brief. For more details on what is responsible for the recent cool trend, just how warm it could get next week, as well as timing of the next chance of rain, read below.


WEATHER HIGHLIGHTS:

  • Below seasonal temperatures continue into early next week
  • Spike back up to summer-like warmth could briefly return mid-week
  • Chance for thunderstorms Wednesday as temperatures, humidity increase
  • Stay on top of ALERTS in your area

WHERE DID THE WARM SEPTEMBER WEATHER GO?

ONSunday

The north Atlantic Ocean is currently in a warm cycle and early fall is when ocean water temperatures peak for the year. This extra heat in the Atlantic Ocean helps to strengthen the large region of high pressure (the Bermuda high) just off the U.S. East Coast.

"This often results in a stronger southwesterly flow of warm and humid air into southern Ontario. That is one of the key reasons to why we have been in a pattern of summer weather lasting into September during recent years," Weather Network meteorologist Dr. Doug Gillham explains.

This year however, the jet stream pattern across Canada has also been delivering an abundance of chilly weather into Central and Eastern Canada.

"So far during September that has been the more dominant pattern and has overwhelmed the warm air that has often been nearby just south of the border," adds Gillham.

IS SUMMER OVER? OR WILL WE SEE THE WARMTH RETURN?

With southern Ontarians getting back into the school and work routine, the cooling weather conditions are more aligned with the fall season. So, is it safe to write off summer completely and expect autumn to take over?

ONMonday

According to Gillham, you won't need to expect winter tomorrow. In fact, quite the contrary, as "very warm and humid" weather will briefly return to southern Ontario on Wednesday with highs in the upper 20s. Some models even have temperatures topping 30°C, for the extreme southwest, where humidex values could return and approach 40°C.

However, with that comes the threat for scattered thunderstorms, as the next system moves in.

ONWed

"Warmer weather is expected for next weekend and into early next week. We have the potential for a more extended period of late summer weather, but confidence is still low as whether the warm front lifts to our north or if it will stall over our region and keep the hot weather just to our south," adds Gillham.

ONThurs

WATCH BELOW: DORIAN RECAP - DOWNED TREES, CRANE COLLAPSE, FLOODING

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