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Ontario: Full sunshine, hot temps to be disrupted by remnant tropical moisture

Thursday, September 19th 2019, 8:30 am - Surging late-summer heat will threaten temperature records for parts of Ontario.

A ridge of high pressure has begun to steer heat and humidity from the southern U.S. back into Ontario for the second half of the week, and that may leave some new record highs in its wake. After a toasty Wednesday in the north, the south will follow closely behind as humidex values climb into the mid-30s into the weekend. We track the heat, where records might fall and when the remnant tropical moisture from Imelda puts an end to this sunny streak, below.

Visit our Complete Guide to Fall 2019 for an in-depth look at the Fall Forecast, tips to plan for it and a sneak peek at the winter ahead


WEATHER HIGHLIGHTS:

  • Temperatures rise into latter half of week
  • Mid-30s humidex values likely for south by weekend
  • Cooler temperatures arrive with fall on Monday

WATCH BELOW: TRACKING THE RIDGE

A strong ridge of high pressure stretching from the Maritimes to the Gulf Coast served as a conveyor belt of warm air aimed right at northern Ontario for Wednesday, where above-average temperatures were the norm.

The south was also warm Wednesday, with more of the same ahead for Thursday. Daytime highs in the low-to-mid 20s will feel slightly warmer with the humidity.

Ontario south

That warmth will only continue to build as the main axis of the ridge shifts east to close out the work week, putting the main push of heat and humidity into southern Ontario.

Temperatures feeling like the mid-to-upper 30s will have those in southern Ontario firing up the air conditioner again beginning on Friday, with the heat expected to peak on Saturday.

onfeelssat

The last few days of summer will feature humidex values more appropriate for late-July than late-September.

PERIOD OF WIDESPREAD RAIN ON SUNDAY WITH REMNANT MOISTURE FROM IMELDA

By Sunday, there's an increasing threat for rain showers and thunderstorms, putting an end to the stretch of this late summer sunshine. That's in part thanks to some remnant moisture from what was once tropical storm Imelda that's bringing flooding rain to Texas.

"While the actual tropical system itself will have long dissipated, a separate low pressure system developing over the U.S. will draw the ex-system's moisture in, leading to higher rainfall totals in parts of Ontario this weekend," says Weather Network meteorologist Kelly Sonnenburg.

ImeldaOntarioRain

Cooler temperatures are also expected to arrive with fall on Monday as a cold front cuts across the province; a front which may also bring showers and thunderstorms for the first day of the new season.

WATCH BELOW: CAN TEMPERATURE SWINGS BRING ON ILLNESS?

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