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The sweltering Ontario heat is expected to tie records, but will they break?

Friday, July 10th 2020, 8:19 am - The province is experiencing a consecutive streak of July days above 30°C, but will it be enough to set a new record for the most-ever number of July days at that temperature?

For those of you that live in Ontario, you don't need a thermometer to tell you it's blisteringly hot and humid -- a couple of minutes outside will do the trick.

And in fact, looking at the stats, the hot and dry conditions may not only put us on track for a shot at breaking some records, they're also building on a period of well below seasonal precipitation that began weeks ago for many.

Visit our Complete Guide to Summer 2020 for an in-depth look at the Summer Forecast, tips to plan for it and much more

Presently, a ridge of high pressure has been the dominant weather player in Ontario since July began, with temperatures of around 8-10 degrees above-seasonal normals. Daytime highs across the province have sitting at or above the 30-degree mark, with the humidex making it feel over and above this -- close to or above 40 in some places.

Temp anomalies July

So, how does this hot pattern compare to normal? Is this a heat wave, and how long will it last?

Firstly you should know that in Canada, 'heat wave' has a specific definition, loosely defined as three consecutive days of at least 32°C. That term, however, has gone by the wayside somewhat, superseded simply by 'heat warning' by Environment and Climate Change Canada.

That varies by province. In Ontario, it is defined as:

  • EITHER two or more consecutive days of daytime highs at least 31°C or nighttime minimums higher than 20°C
  • OR two or more consecutive days of humidex values of 40 or higher

heat warning

We are entering Day 9 of consecutive 30°C temperatures for Toronto, with signs of temporary relief, which will tie the record, but will it hold out so a new one can be set?

Now, long hot stretches have happened before. In fact, going by data from Toronto's Pearson Airport, 1955 feature 19 days above 30°C, while the record for most consecutive days was set in 1999, which featured a nine-day stretch in late July:

Updated Ontario stats

Friday is expected to be the ninth, and final day of the streak, so, while it has been impressive, it will not sustain itself long enough to shatter records. On Saturday, temperatures in Toronto will dip a few degrees below 30, and thus, ending the spell.

Fret not, the break from the heat this weekend is forecast to be short-lived and temperatures will soar again next week. Who knows, perhaps another consecutive streak of 30°C days in July will commence.

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