A powerful storm that swept through southwestern Quebec on Thursday produced record rainfall, flash flooding, and at least one tornado on the territory -- possibly two.

Environment Canada estimates that between 50 and 100 millimetres of rain fell in the Montreal region alone, with 82 mm recorded at the McTavish weather station near McGill University. This more than doubles existing rain records for July 13, the highest being 34 mm recorded at the Montreal airport in 1997.

Speaking to CTV News, Environment Canada spokesperson Simon Legault could not confirm whether Thursday's rainfall breaks the all-time, single-day record, but said it at least comes close. 

He said Montreal received nearly a month's-worth of rain in just a few hours. 

At least one tornado was recorded in Quebec. The funnel clouds touched ground Thursday afternoon in a field near Mirabel, about 50 kilometres northeast of Montreal.

Environment Canada is also investigating a second possible tornado, this one southwest of Montreal in the Salaberry-de-Valleyfield area.

No injuries or damage were reported in either case.


A city spokesperson said Friday that Montreal needs to do more to mitigate the effects of extreme weather events.

Philippe Sabourin told reporters that the storm triggered the city's first tornado warning that brought wind gusts of 100 kilometres per hour and torrential downpours that flooded about a dozen underpasses and more than 100 homes.

Some drivers had to abandon their cars after being caught in the middle of flash floods.

To help deal with future weather events, the city should build "immense" underground reservoirs to store excess water and build more green spaces like parks and gardens so that they absorb rainfall.

"The idea is to build a sponge city," Sabourin said.


Montreal was under a tornado warning for part of the day, something experts described as exceedingly rare -- but the warning was downgraded to a tornado "watch" by the early evening, with no twisters in sight (just lots and lots of lightning, thunder and rain).

The same can't be said for Ottawa, however, where a tornado damaged over 100 homes in the south-end suburb of Barrhaven. No injuries were reported.  

Torrential rains in Montreal caused flash floods in at least 15 of the city's underpasses. Decarie Boulevard was temporarily closed in both directions due to flooding, as was the Square-Victoria-OACI metro station. 

The downpour knocked out power for hundreds of thousands of Hydro-Quebec customers. About 200,000 remained without electricity early Friday morning. 

With files from The Canadian Press


A previous version of this article reported a total rainfall of 38.6 mm in Montreal on Thursday. This measurement was recorded at the airport, whereas measurements taken at McTavish station showed a much higher rate (82 mm).