Parts of southern Ontario see hottest temperatures of 2023, more heat to follow

Ontario is in the midst of its hottest stretch of summertime heat as we settle back into the September routine, and it’ll be a few days yet before relief is on the horizon.

It was the warmest day of the year for many locations across Ontario, including the warmest September day since September 5, 2018 for Toronto. Although Pearson International Airport was the hottest location in Ontario, other locations easily surpassed 30°C. Communities that exceeded 30°C include Burlington, Hamilton, Peterborough, Sarnia, and Windsor to name a few.

Toronto Temp Sept 4 2023
Toronto Temp Sept 4 2023

A similar calibre of warmth is forecast on Tuesday, with most regions of southern Ontario spilling into the low 30’s for the third straight day. Although temperature anomalies are 8-10°C above normal in the south, areas near James Bay are forecast to soar over 15°C above seasonal on Tuesday, before a sharp temperature plunge on Wednesday.

LOOK AHEAD: Warm or cool? Reversing patterns to dominate Canada in September

Sinking air beneath our growing ridge, combined with bright sunshine and humid winds blowing into the region, will lead to an extended spell of warm and muggy conditions across the entire province through the first half of the week.

ON temps tues sept 5 2023
ON temps tues sept 5 2023

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Daytime high temperatures will likely crack the 30-degree mark several days in a row for many communities. Forecasters expect most major cities, including Toronto and Ottawa, to see their longest stretch of 30+ degree highs of the summer through this week.

Toronto’s latest forecast calls for four days in a row of 30°C or warmer, besting the previous streak of three days hitting the mark.

ON Air quality sept 5 2023
ON Air quality sept 5 2023

All this hot, muggy air means air quality has degraded across much of southern Ontario, hovering in the moderate category for millions of people on Tuesday.

Similar levels of air quality were reported in mid-August–a far cry from the record-breakingly bad air quality in late June from the unprecedented wildfire activity in Quebec.

WATCH: Humidex records fall in northern Ontario as September heat broils the region

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RELATED: The importance of staying hydrated in warm weather

While this week’s forecast is perfect for those who never want summer to end, the muggy conditions and bright sunshine carry dangers of their own.

It’s easy to overdo it in heat like this, especially with feels-like values creeping beyond 40 at times throughout Ontario. Even the fittest folks are susceptible to heat-related illnesses.

Heat Stroke and Exhaustion Symptoms
Heat Stroke and Exhaustion Symptoms
  • Drink plenty of water even before you feel thirsty and stay in a cool place.

  • Check on older family, friends and neighbours. Make sure they are cool and drinking water

  • Never leave people or pets inside a parked vehicle.

  • Outdoor workers should take regularly scheduled breaks in a cool place

The arrival of September marked the start of meteorological fall, though the autumnal equinox doesn’t officially occur until the wee morning hours of Saturday, Sept. 23.

Join us for the release of our 2023 Fall Forecast on Wednesday, Sept. 13. Our experts will take a look at temperature and precipitation trends for the upcoming season, revealing what you can expect during this highly changeable season across Canada.

WATCH: What longer, hotter, and more frequent heat waves means for your health

Click here to view the video

Thumbnail courtesy of Warren Wong on Unsplash.

Stay tuned to The Weather Network for more forecast updates for Ontario.