Why Toronto's second heat wave of July isn't that unusual
· Toronto Sun
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Toronto was on its way to setting a heat record on Tuesday with maximum temperatures expected to hit 37 C and feel more like 45 C with the humidex, although there was nothing unusual about the city’s second heat wave so far in July.
The first heat wave, which saw Environment Canada issue an orange warning, was from June 30 to July 4.
The most recent heat event, which saw the lesser yellow warning issued, started Monday. It was supposed to end by Wednesday or Thursday night with Tuesday being the hottest day.
“We certainly have done it before,” The Weather Network meteorologist Doug Gillham said.
“The previous heat event, I mean, the humidex peaked at 48 C at Pearson; now that is unusual, but to have two heat events in July is not unusual. It is true that both events have pushed the upper limits of typical Toronto heat. So 48 C humidex is brutal, but the record is 50.3 C (set in 2011), so we came up (short).”
Daily record still in sight
Still, Gillham said Tuesday’s high was about 10 C above the seasonal average and the daily record-setting high temperature for Toronto is 36.8 C (set in 1995).
“Our forecast is to reach 37 C, so if we reach the forecast, we break the record. But if we were only to get to 36.5 C, which would still be a pretty good forecast, we wouldn’t even have a daily record,” he said. “So it’s exceptionally hot, for sure. To put it in perspective, Toronto Pearson has only been warmer than 37 C only six times on record, so (Tuesday) there were models calling for 37-38 C, so we’ll just have to see how warm Tuesday gets.”
Gillham said numerous factors were causing the latest heat event, including a heat dome to the west.
“(A) strong area of high pressure in the mid and upper levels of the atmosphere,” he said. “It’s a lot of sinking air. When air sinks, it heats up and that has spread east. This is a pretty short heat wave for Toronto. It’s one day of extreme heat. Whereas we had several days with the previous event where we had the humidex in the mid-40s.
“What’s most exceptional is Armstrong, Ont., which is way north and there’s no urban heat influences there. They got to 40.8 C (on Monday), so that is historic for them.”
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Relief expected soon
The heat wave was forecast to end Tuesday night for some regions in central and northeastern Ontario, but persist into Wednesday or Thursday for areas in southern Ontario.
“Wednesday will not be as hot as Tuesday, but it’ll still be over 30 C in terms of the actual temperature,” said Gillham.
Gillham also predicts Toronto will get a third heat wave in early August.
“I think the week where we transition into early August, I’m watching for another potential heat wave,” he said. “It’ll probably only be a few days. But I think most of August will be near normal, so you get these high-impact heat events, but they’re relatively short-lived and they don’t dominate the summer.”