Ottawa records hottest July since 1921
OTTAWA -- It was not just your imagination. This July was the hottest in Ottawa in nearly 100 years.
Ottawa sweltered under intense heat waves for more than half of the month. There were four heat warnings issued in July, one of which lasted for five straight days. Eighteen days saw highs above 30°C, including three days that broke high-temperature records, and there were six nights where the temperature didn't fall below 20 degrees.
Speaking on CTV Morning Live on Friday morning, Environment Canada Senior Climatologist David Phillips declared July 2020 the hottest on record in the nation's capital, according to data collected at the Ottawa airport.
Phillips says they look at three temperatures: the average of all afternoon highs, the average of all overnight lows, and the average for the whole month.
"In all three accounts, Ottawa International Airport broke the record for the warmest July. The afternoon highs were almost four degrees warmer than normal. The lows were about two degrees warmer than normal, and the daytime—stick a thermometer in the capital—and it was about three degrees warmer than normal."
The average high for July 2020 was 30.5°C, while the average low was 17.4°C. The mean temperature for the month was 24.0°C.
Based on data from Environment Canada's website, collected at the Ottawa airport, the previous average high temperature record was 30.3°C, set in 2012; the previous record for the highest low temperature was 17.1°C, set in 1988; and the mean temperature record was 23.6°C, set in 1955.
Heat records were broken on July 9, 10, and 26, with high temperatures of 35.8°C, 36.9°C, and 35.5°C respectively.
The number of nights above 20°C, which Phillips called "tropical nights", was triple the normal amount.
"You had six tropical nights, you normally see two of them," he said.
May and June also had temperatures above 30°C.
"I guess the capital was 'well done' when you stick a thermometer in it this past July."
1921 records still stand
The airport records date back to 1938. Older records from the Central Experimental Farm do show at least one July hotter than 2020.
In 1921, there were 20 days at or above 30°C. The average high in 1921 was 31.4°C, the average low was 18.5°C, and the mean temperature was 24.9°C.
Citizens of Ottawa also sweated through 12 nights with lows at or above 20°C.
Experimental Farm records date back to 1889.
Heat dome to blame
Phillips blamed July 2020's weather on a heat dome stuck over eastern North America, with Ottawa in the centre.
"This air doesn't move," he said. "You're breathing the same air on Friday that you were breathing on Monday. It doesn't circulate. There's no fresh, Canadian air coming in. It's compressed air. It's sinking from the upper levels down to the surface and all those molecules of air jiggle and jaggle and warm up and collide into each other and create heat."
It's also been dry, with Ottawa seeing just about half of the normal amount of precipitation over the last two months, Phillips said.
August starts cool but expect more hot days
The forecast for the first week of August starts with cooler than average temperatures and several days with showers in the forecast, but Phillips said we shouldn't get too comfortable.
"We're going to be counting these days above 30 right through to Labour Day," he said. "Our models show, for Ontario, Quebec, warmer than normal in August."
Phillips noted that August is typically about one degree cooler than July, on average, and he doesn't expect any heat records, but August will still feel much like July.
"It's going to be the same pattern. We don't see a break down at all. It's going to be the summer of summers: a bummer for some and a hummer for others."