Published on August 6, 2025 at 9:53 p.m.
After two months already marked by sustained heat, August 2025 may well become the highlight of summer in Quebec. Explanations.
Generally second August, but not always
On average, August is about a fresher degree than July, but this is not always the case. Since 1942, there have been 14 summers when August was the hottest month of the summer season in Montreal (excluding 2003). In more than half of the cases (8 out of 14), this occurred during fresher summer than normal.
“During fresh summers, especially if the season is slow, it will happen that the month of August is the hottest of summer, without it being enough to save the summer,” says Réjean Ouimet.
New trend
The scenario of a month of August at the top of the bill in a generally hot summer is no longer as rare, however. Since 2000, this has happened three times (in 2001, 2010 and 2021), as much as during the previous 58 years. Recent hot summers therefore seem more inclined to see August fly the show.
Heat waves, a key engine
Among the 14 months of August summer winners, 9 experienced at least one heat wave (three consecutive days when mercury indicates 30 ° C or more) in Montreal, twice as much as normal frequency. In 2021, two heat waves had helped to propel August at the top. In 2001, a heat wave had stretched over 10 days.
“If it is not guaranteed to know a heat wave in August, for the month to be declared the champion of the summer, a heat wave will help a lot,” says Réjean Ouimet.
The current scenario for the beginning of August 2025 suggests that a significant heat wave, or even a heat wave, could be at us.