Cars were caught in flooding at L'Acadie Circle. (CBC)Flooding, collapsed walls and power outages were reported as severe thunderstorms hit the Montreal region Friday afternoon.

Several flights arriving at and departing from Trudeau airport were also delayed.

A cold front passing through the region was expected to provide Montrealers with a short break in the heat wave that has blanketed the city for four days.

Flooding was reported in several areas of the city and water created problems for drivers on some busy highways.

Lanes were closed because of flooding at L'Acadie Circle, an exit ramp off busy Highway 40 in central Montreal.

At least three cars were caught in the water in the underpass, which has been notoriously prone to flooding during heavy rainfall since its reconstruction in 2005.

Water accumulation also stranded cars under the De Salaberry overpass on the Laurentian Autoroute and surprised drivers on St-Laurent Boulevard near Chabanel Street, who returned to find their cars swamped.

Strong winds created problems in the city's Plateau district, where two pillars that had been supporting banners collapsed, Montreal police said.

Both incidents occurred on Laurier Street — one near the corner of Park Avenue and the other near Saint-Urbain Street.

In one case, falling bricks from a wall struck a woman, leaving her with minor injuries, said Const. Yannick Paradis.

Flooding of streets was also reported on Montreal's West Island.

Montreal Mayor Gerald Tremblay said 66 millimetres of rain fell in less than an hour.

"It is as if the equivalent of two thirds of the rain that fell normally falls in the month of July," said Tremblay.

He said city officials were following the situation closely and would intervene as required.

Hydro-Québec reported that about 42,000 households lost power Friday afternoon. The outages were mostly in the Montreal, Montérégie and Lanaudière regions.

Officials said they could not confirm when electricity would be restored since more storms were expected.

Two walls on Laurier Avenue collapsed during strong winds Friday afternoon. (CBC)Temperatures dropped by about 10 C as a line of storms passed over Montreal early in the afternoon.

The storms also hit regions north and south of the city.

"There are some cells that are developing behind so there will likely be more storms later this afternoon," said Environment Canada meteorologist André Cantin. "The rain should gradually drop off overnight … to bring us a pretty nice day tomorrow with clearing skies in the morning and temperatures that are much more comfortable."

'It's going to come to an end but not before a … sound and light show.' — David Phillips, Environment Canada senior climatologist

Meteorologists had forecast that more than 50 millimetres of rain could fall in less than an hour, which could lead to flooding.

Thunderstorm warnings were also in effect for the Eastern Townships and the Saguenay and Quebec City areas.

On Thursday, the city broke heat records for the third straight day. The temperature in Montreal rose to a record high of 33.4 C, breaking the previous high set in 2008.

The break in the hot temperatures is expected to be brief however. Environment Canada said that temperatures could reach highs of 30 C again on Saturday, with overnight temperatures remaining above normal levels of 18 to 20 C.