Utility crews scrambling to restore power to tens of thousands of Toronto residents after last night's record-breaking storm were dealt a big setback on Tuesday afternoon when a supply problem led to 50,000 more customers losing their power.

Toronto Hydro said early Wednesday morning some 16,000 customers across the city were still in the dark after Liberty Village and the surrounding area in the city's west end were affected by a lack of supply from a Hydro One station.

As the city struggled to dry out from the wicked storm, which turned downtown streets into lakes and flooded subway stations, Mayor Rob Ford urged residents to reduce power consumption and weather forecasters warn about more rain ahead.

"What occurred over a few short hours last night was unprecedented," Ford told reporters at a news briefing, referring to the 126 millimetres of rain that fell on the city in just two hours last night.

The downpour was more than the amount of precipitation Toronto would get in an average July. The torrential rain and squalls downed trees, flooded subway stations and basements, and stranded motorists in murky waters.

David Phillips, a climatologist with Environment Canada, said those rains may have been "the most intense, wettest moment in Toronto's history."

As crews began the cleanup today, thousands of Torontonians remained in the dark.

"Toronto has persevered; we have weathered the storm," Ford said, before stressing the need to reduce electricity consumption over the next 24 hours.

"This is crucial that we all reduce our electricity for today to help relieve the strain on our hydro system. We're hanging on by a thread right now," he said.

Toronto Hydro says customers in four major areas will be affected by "load shedding," which means planned rotating blackouts. Those three areas are:

North of Nassau Street, south to King Street West; West of Shaw Street, east of Charlotte Street.

South of St. Clair Ave West, south to Queen Street West; west of Jane Street east to Spadina Avenue.

Dundas St West to Lake Ontario; Roncesvalles Avenue east to Spadina Avenue.

Old Weston Road, south to Queen Street West; Sunnyside Avenue, east to Lansdowne Avenue.

Reiterating the mayor's plea for power conservation, Toronto Hydro CEO Anthony Haines called on citizens to unplug nonessential lighting and electronics. Haines said customers must shed the city's hydro load by about 200 megawatts — the equivalent amount of power needed to run about 200 large condominium buildings.

Toronto Mayor Rob Ford asked people to limit their electricity use on Tuesday, as thousands of city residents were still without power. (CBC)

"The system is operating beyond its operating capacity as I stand in front of you right now," Haines said, noting that city hall is doing its part to only keep air conditioners running if necessary.

"As you can feel, it's starting to get muggy in here," he told reporters. "And that's because the city has feathered back all of its critical loads."

Ford said he'll be meeting soon with city manager Joe Pennachetti to discuss the city's emergency response to the flash flooding "so we can fully understand what worked and determine what needs improvement."

Search for missing 76-year-old

Pennachetti has been tasked to complete a review. He said the city's 311 hotline logged 1,000 calls about flooded basements in a period of four hours.

Ontario Premier Kathleen Wynne has already reached out to the mayor and praised the cities of Toronto and Mississauga for their handling of the crisis.

"From first responders, city employees and hydro crews to the generosity of men and women checking on their elderly neighbours and the patience of those who shared their snacks on the stranded GO train, Ontario residents have demonstrated great endurance, resilience and good humour," she said in a statement.

Police said they are searching for a missing 76-year-old man last seen around 8 p.m. in the Yonge Street and Finch Avenue West area. The man, identified as Walter Thompson, is between five-feet-six and five-feet-nine inches tall, weighing about 160 pounds, with grey hair. Thompson, who wears glasses, was last seen wearing a red long-sleeved shirt with dark blue pants and black shoes.

He may have been driving a grey four-door 2007 Chevrolet Malibu with Ontario licence plate 245 WCB.

Meanwhile, Toronto is bracing for more rain. CBC meteorologist Jay Scotland said possible thunderstorms forecast for the Greater Toronto Area could create the possibility for more heavy downpours.

"There is the risk for thunderstorms in southern Ontario with the humidity today. A better chance for severe weather tomorrow for Toronto and the lower Great Lakes," Scotland said.

He noted that Monday's downpour "even topped Hurricane Hazel's one-day rainfall total going back to 1954," noting that the amount that fell then was 121.4 millimetres.

Toronto and surrounding cities battled the extreme weather on Monday as riverbanks spilled over onto roadways creating delays for commuters. High winds also knocked out power to some areas, leaving thousands without electricity overnight.

Hydro One said that of about 300,000 people affected, only about 30,000 to 40,000 had their power restored as of midnight ET due to "significant flooding" at two of its transmission stations.

Train stranded

About 1,400 people were caught by the flooding aboard a northbound GO Transit train, and it took police and firefighters about seven hours to ferry everyone to dry ground aboard small inflatable boats.

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The operation ended at about 12:30 a.m. Authorities said five or six people were treated at the scene for minor injuries. Go Transit said the storm left portions of track "completely under water" on its Milton, Richmond Hill and Lakeshore West lines and suggested passengers seek alternative ways to travel Tuesday morning.

This morning, a commuter reported that shuttle buses were being used on the Lakeshore West GO Train line between Port Credit and Long Branch to move passengers past a flooded area.

Toronto police Const. Wendy Drummond said she's never seen a flooding incident this severe in the city, but emergency crews were prepared to respond.

"Somebody looking at the scene may not understand everything that is happening, but rest assured that efforts, emergency response efforts, have been in the planning stages from the very onset," she said.

Two people attempted to flee by jumping out the train and swimming to shore. Rescuers had to pluck one of them from the murky water.

'Tremendously concerned'

The rain left underpasses and many basements flooded and a number of people trapped in vehicles — some with water up to their vehicle windows.

George Newman was driving to his friend's 80th birthday party under the heavy downpour when his car became submerged. "The water was up to my stomach in the car and the power just shut off," Newman said. "There were men going into the cars to get us out and lift a few of the people that couldn't get out."

Speaking on CBC Radio's Metro Morning on Tuesday, Coun. Denzil Minnan-Wong, who heads the city's Public Works and Infrastructure Committee said he was "tremendously concerned" about the impact of the storm.

"If you have Hurricane Hazel having happening every couple years we're going to be a lot more trouble than we ever imagined," said Minnan-Wong.

Public transit users wait for shuttle buses at Jane Station in Toronto's west end. A section of the subway line was closed because of severe flooding at one of the stations. (Trevor Dunn/CBC)

Electrical issues on traffic cameras made tracking troublesome areas difficult for city officials, but Minnan-Wong said identifying improvements would part of the coming days. He praised all those involved in the rescue and cleanup efforts.

"When you think about what happened just 12 hours ago, it could have been better, but I think it could have been a whole lot worse," said Minnan-Wong.

"If you don't pay attention to it, these storms are going to have a lot of damage to a lot of city infrastructure and particularly to a lot of families throughout this city who are waking up to flooded basements."

TTC delays

Toronto Transit Commission Chair Karen Stintz advised the to public move slow and steady, treating it as a "summer snow day."

Extra TTC staff were on site this morning at Jane station in the city's west end, where a major stretch of the east-west subway line was shut down due to heavy flooding at Kipling station.

As many as 70 buses were going back and forth between Jane and Kipling, helping to move the thousands of commuters who use the line every day.

The CBC's Trevor Dunn said Jane station was busy, with some confusion, but that shuttle buses were running continually.

The TTC worked through the night to repair the damage at Kipling, but there was simply too much water in the underground station.