More heavy rain and thunderstorms expected across Greater Montreal Sunday afternoon

After major flash flooding on June 20, 2026, basements, streets and a grocery store were flooded on Montreal's West Island.

Environment Canada says more heavy rain and thunderstorms are expected on Sunday in the Greater Montreal region, one day after flash floods caused widespread flooding in several areas.

Greater Montreal is expected to receive between 25 and 50 millimetres of rain between noon and 9 p.m.

Antoine Petit, a meteorologist for Environment and Climate Change Canada, says yesterday’s downpour was localized in areas such as the West Island, the South Shore and Laval West, receiving up to 150 millimetres of rain in a short period of time.

West Island among areas hardest hit

Dollard-des-Ormeaux, Pierrefonds-Roxboro and Pointe-Claire were hardest hit, Petit told CTV News.

“It shouldn’t be as intense as yesterday, but we need to keep an eye on the warnings in the afternoon for heavy rainfall,” he said. “Hopefully, the rain won’t fall over the same areas as yesterday.”

According to Petit, the Laurentians are already experiencing heavy rain and lightning, and the storm is expected to continue moving south toward Montreal.

On the South Shore, Candiac, Saint-Constant and Sainte-Catherine were among the areas hardest hit by Saturday’s weather, which brought approximately 100 milimetres of rain.

Petit says Laval West also received about 100 millimetres of rain on Saturday.

In contrast, downtown Montreal and the Laurentians received about 15 millimetres of rain on Saturday.

Low-pressure system over Quebec

Petit says the recent weather in the Greater Montreal area is the result of a low-pressure system moving across Quebec and Eastern Canada.

“When we see a dominating trough pattern over the province, it means we’re going to see days with more clouds, showers, and thunderstorms here and there, so it’s going to be more unstable, and the days tend to look less like summery,” he said.

“We have a lot of trough over the province that creates instability during the afternoon hours, so that’s basically why we see a lot of rain and unstable weather recently, rather than sunny and warm like a lot of people wished.”

Petit says the weather system will continue to affect central Quebec and the Quebec City region this week, while conditions in the Greater Montreal area are expected to gradually improve.