Thousands of people are without power and flash flooding has been reported across Toronto after severe weather slammed the city this afternoon.

A heavy thunderstorm passed through the city for about an hour Wednesday, swelling waterways, downing trees and flooding basements.

According to the Toronto and Region Conservation Authority, the storm dropped about 65 millimetres of rain on some areas of the city within about half an hour.  

Video sent to CP24 showed dozens of cars half-submerged in water in a parking lot near Eglinton Avenue and Caledonia Road. Basement homes in the area were also reportedly flooded.

Const. Alex Li told CP24 that 911 and emergency services have been “inundated” with a flood of calls for service about downed trees, fallen wires and flooding.

“Although we understand that those are concerns for our residents in the city, we want to reiterate to please contact 311 and utilize that resource to rectify these issues. We don't want our 911 lines to be tied up with non-emergency calls,” Li said.  

“Trees down, wires down or flooding should go directly to 311. However, if you do see anything that is a public safety issue with regards to a sparking wire or a transformer that might be exploding or on fire due to the rain then please utilize 911 and we will respond with emergency services."

Environment Canada said the storm was capable of producing strong wind gusts and rainfall accumulation of between 50 and 70 millimetres.

"Wind gusts up to 100 kilometres per hour are likely on the west side of Toronto," the weather advisory read.

The storm also briefly triggered a tornado watch for the city, but it was cancelled at around 3:13 p.m., roughly 25 minutes after it was issued.

"It is moving very quickly but at the same time, it's severe and it's giving a lot of rain.... in a very short amount of time," Environment Canada meteorologist Gerald Chang told CP24 as the storm was still raging.

"When we're talking about that rainfall amount, around 80 mm of rain is really the monthly rainfall for Toronto so this is quite significant and it could lead to flash flooding."

He noted that the "isolated" storm was mostly impacting the city's west end.

In the area of Keele Street and Lawrence Avenue, police received reports of a car floating away and a person in a canoe on the roadway.

Police also said the city's Black Creek River has "broken banks in several places" and townhomes in the area of Weston Road and Humber Boulevard might need to be evacuated due to possible flooding.

Toronto Hydro is reporting scattered outages across Toronto due to heavy rain and high winds. About 1,800 customers remained without power as of 11 p.m.

At the peak of the storm, around 45,000 customers didn't have power.

"It was a flash storm. It came in really quickly," Toronto Hydro spokesperson Mallory Cunnington told CP24. "But the damage that we've seen is extensive. We've seen power lines down, trees down in the area."

She said the most of the outages are in the city's west end.

"We do hope to restore power to a big chunk of customers tonight. However, there will be customers that will remain without power throughout the night and into tomorrow," Cunnington said.

"We are doing everything we can to restore power."

The storm and outages come as Toronto continues to sit under a heat warning. Temperatures have consistently been above 30 C in the city this week. A high of 30 C was forecast for Toronto Wednesday evening, but it feels more like 37 with the humidity.

Scorching conditions continue on Thursday and Friday with a high of 35 C and 33 C, respectively.