The Toronto area was drying out Tuesday morning after record rainfall the night before closed transit and roadways, stranded commuters knocked out power in several areas, flooded homes and caused other damage.

Environment Canada said some parts of the GTA had been drenched with more than 100 millimetres of rain, trouncing the previous one-day rainfall record of 29.2 mm in 2008 for Toronto and even beating the 74.4 mm monthly average for July.

Water from flash flooding poured out of sewer drains while Toronto's downtown core was dotted with abandoned vehicles, some sitting in water up to their windows. One woman, sporting a T-shirt and shorts, dove head-first through the window of her marooned car before wading away in the thigh-deep currents.

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Mayor Rob Ford encouraged people to stay inside their homes where possible, except to check on the vulnerable, elderly, or those who may not be able to cope on their own.

He said the city is taking an "all hands on deck" approach to dealing with the "serious situation" caused by the first round of storms. He said civic officials are bracing for the second round now nearing the western end of the GTA.

He asked Toronto residents not to call 911 unless it's a dire emergency because the line is getting overwhelmed. He urged people to contact 311 for information updates.

Toronto Hydro reported approximately 300,000 customers were without power across Toronto by 7:30 p.m. Monday.

About 35,000 of its customers were still without electricity as of about 3 a.m., primarily in the west end of the city, Toronto Hydro said.

Milly Bernal, a spokeswoman for the Toronto Transit Commission said that some stations are flooded and some are operating with emergency lights.

Ms. Bernal said Yonge-University-Spadina line is closed from Downsview station to St. Clair, St. Andrew to Bloor, and from Lawrence to Finch. The Bloor line has been shut down from Jane to Kipling, and the entire Sheppard line is out of service.

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Porter Airlines has cancelled all Toronto flights for the rest of the day because of the storm and power outages at the airport. The airline tweeted that passengers will be accommodated on flights tomorrow, and that high call volumes are causing longer than average wait times at their call centre.

Between 30 and 40 millimetres of rain had fallen by 6:15 p.m. with another 10 to 15 expected this evening, Councillor Denzil Minnan-Wong said, based on reports from the Toronto and Region Conservation Authority.

"We are receiving significant reports of basement flooding," Councillor Minnan-Wong said. Underpasses in the downtown are also flooded, he said.

Road closures include the Don Valley Parkway between Bloor Street and the Gardiner and Allen Road northbound at Eglinton, he said.

Mobile phone and text service was down for numerous Rogers and Fido customers in the region Monday night, making it difficult for many caught in the storm to reach loved ones. Rogers spokesperson Patricia Trott confirmed that the service interruption was related to the severe weather battering the area, but could not confirm the number of people affected by the outage. "We apologize to our customers and are working to fix the problem as soon as possible," she said. Mobilicity customers also reported outages.

Pockets of the downtown core were also rife with gridlock, as many intersections, including in the Queen-Bathurst area, had no police on hand to direct traffic.

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Small, street-level retail businesses, many lacking the backup power afforded by larger companies, faced some of the worst consequences of the outages.

Jeff Caires, owner of the Tequila Bookworm restaurant and bar at Queen Street West and Portland Street, said he hadn't seen rain so bad in the more than seven years he'd been at the location.

"I've never seen anything like this," Mr. Caires said. While the basement wasn't flooded, he said the shop's backyard was.

While some power was restored in the area at about 7:30 p.m., there were still some stretches affected further west downtown, including on Queen Street near Trinity Bellwoods Park. The park's off-leash "dog bowl" section, located near a ravine, had turned into a veritable lake with water nearly a foot deep in some places.

"We're currently facing significant system issues," said Andrea Corkum, a Hydro spokesperson. "There are so many outages everywhere."

All of Toronto Hydro's crews are currently out making repairs and they will likely work throughout the night, focusing on the largest outages first, according to Ms. Corkum.

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GO Transit spokeswoman Vanessa Thomas said that flooding on train tracks is affecting trains between Toronto Union Station and Richmond Hill.

TTC chair Karen Stintz posted a photo on Twitter showing ankle-deep water in Queen's Park subway station saying "thank you for your patience. TTC is working hard."

Reached late Tuesday night Councillor Doug Ford said he directed traffic for four hours in Etobicoke. "Absolutely," he said in a message. "Everyone was helping."

With files from Josh O'Kane and the Canadian Press