Hundreds of thousands of customers lose power in Quebec as ...

Nearly half a million households were in the dark Friday as remnants of Tropical Storm Debby wreaked havoc on southern Quebec.

In Montreal, several roads were washed out, basements were flooded, and the city's light rail network, the REM, was completely shut down due to a power outage as heavy rainfall hammered the region.

Environment and Climate Change Canada (ECCC) said more than 150 millimetres of rain had fallen as of 9 p.m., just as a rainfall warning for the area had ended. That broke the all-time daily record set in 1996.

Montreal gets an average 94 millimetres of rain during the entire month of August.

As of 10 p.m., Hydro-Quebec was reporting more than 460,000 customers lost electricity. The hardest hit areas were the Montérégie region (210,000), Montreal (75,000), and Laval (55,000).

Flooding in Montreal on Aug. 9, 2024 as the remnants of Hurricane Debby hits the region. (Angela MacKenzie, CTV News)

The power utility said the outages were caused by wind gusts and fallen tree branches on the power grid during the powerful storm and crews were out in the field trying to restore power.

Cars drive slowly through water overflowing on to highway 40 in Sainte-Anne-de-Bellevue on the island of Montreal after heavy rains hit the area on Friday, August 9, 2024. THE CANADIAN PRESS/Peter McCabe

"We are mobilizing all available crews to work tonight, and are issuing a massive recall to ensure we can count on a good strike force by 5 a.m. Saturday morning," reads a statement on its website.

"We are giving restoration times to the best of our knowledge at this stage, but these times may vary greatly depending on the damage observed and the nature of the work required to restore power service."

Hydro-Quebec spokesperson Louis Olivier-Batty told CTV News that the vast majority of households will have their power restored by Saturday morning, but some could be waiting until later in the day or possibly into Sunday before the electricity comes back.

"We do understand it's not a nice situation for our customers. We thank them for our comprehension and our crews will work hard tomorrow," he said in an interview. 

About 100 crews were out in the field Friday night and hundreds more will be deployed Saturday morning, he added. 

The storm merged with a low pressure system over the Great Lakes and moved across southern Ontario and Quebec, prompting Environment Canada to issue alerts and warnings from Cornwall, Ont., to Quebec City about the risk of flash flooding.

The Lafontaine tunnel, which connects Montreal to the South Shore, was shut down in both directions Friday night, according to the Quebec transport ministry.

The ministry reported several road closures in the Montreal area due to water accumulation Friday evening, including the Décarie north expressway near Royalmount Avenue.

A garage was flooded in Montreal during heavy rains on Aug. 9, 2024. (Angela MacKenzie/CTV News)

In Pointe-Claire, lanes on Highway 20 west near Cartier Avenue were blocked due to flooding.

There was also flooding on Highway 40 near exit 55 to Des Sources Boulevard.

There were several delays and cancellations at the Montreal-Trudeau airport Friday due to the weather.

In Montreal's Saint-Laurent borough, the sounds of generators and pumps filled the streets as residents and businesses tried to keep the floodwaters from building up.

"Today, when we arrived here, the water was just over here and everywhere. Truck was jammed, the car was jammed, and the store was full of water. About eight inches," said Alain Daigle, owner of the Benjamin Moore paint store at the corner of Côte-Vertu Boulevard and Beaulac Street.

A map of the power outages in and around the Montreal area as of 7:30 p.m. on Friday, Aug. 9, 2024, as remnants of Tropical Storm Debby pass over the region. (Source: Hydro-Quebec)

Daigle said in his 35 years of business, the store has never flooded — until last month's record-breaking rainfall and again on Friday.

"We just restored the store … we were supposed to open Monday but I think we'll postpone that again," he said.

Transport Quebec said it had prepared for this kind of weather by removing debris from the road, but when it comes to this amount of rain, no equipment can keep up.

"We have powerful pump systems, they're up-to-date, they're fully functional, but the issue is when we have exceptional amounts of rain like we're having today and we had in July, no storm sewer system can take all of that water," said transport ministry spokesperson Louis-Andre Bertrand.

Cars drive through water on a street during rainfall in Montreal, Friday, Aug. 9, 2024. Environment Canada has issued a rainfall warning for the region. (Graham Hughes, The Canadian Press)

The ministry is urging all motorists to drive carefully during the weather as the storm system passes over the region.

In Saint-Laurent, many homes flooded along Henri-Bourassa Boulevard and Norman Street. Firefighters helped exhausted homeowners pile sandbags and pump basements.

"The water kept coming up. Kept coming up, coming up. And the water overflowed," said Harry Babaroutsis, whose basement was flooded.

Hydro-Quebec said homeowners should be careful if their basements are flooded and to call 1-800-790-2424 to allow crews to cut their power before heading downstairs. 

The deluge of rain forced the cancellations of several events across Montreal, including some outdoor activities for Montreal Pride, including community day in the Village and Soirée 100 per cent Drag at Montreal's Olympic Park's esplanade, which was postponed to Saturday.

La Ronde amusement park also closed, as well the Granby Zoo east of Montreal.

The opening events for the hot-air balloon festival in St-Jean-sur-Richelieu, southeast of Montreal, were postponed until Monday.

The non-profit day shelter, Resilience Montreal, flooded, according to executive director Nakuset.

Nicholas Minas, a convenience store owner in Montreal's Parc-Extension neighbourhood, said he was checking the store's basement for flooding before doing the same in his garage and his mother's basement.

"I have to go downstairs and check every so often just because you never know when it’s going to happen," Minas told The Canadian Press. "When it comes, it comes down and you can see that the sewers don’t necessarily suck it up fast enough."

With files from CTV Montreal's Olivia O'Malley and Caroline Van Vlaardingen, and The Canadian Press