Mayor Rob Ford is urging residents to turn off all non-essential appliances and lights in the wake of major flooding that has left the city’s electrical system ‘hanging on by a thread.’

Ford made the comment to reporters Tuesday morning, one day after a major storm dumped more than 100 mm of rain on the city, triggering serious flooding that temporarily shut down the subway system and left vast expanses of Toronto in the dark.

“Folks, I must stress, and this is crucial, that we all reduce electricity for today to help relieve strain on our hydro system,” Ford said. “We’re hanging on by a thread right now.”

About 126 mm of rain was recorded at Pearson International Airport throughout Monday, breaking a 59-year-old single-day record for the city.

In addition to flooding basements, rail tracks and roads, the rain also left a Hydro One power station that feeds the Toronto Hydro grid under 20 to 30 feet of water.

As of 11:15 p.m., Toronto Hydro said that 31,500 customers were without power.

According to Toronto Hydro, about 11,500 customers in the city’s west end remain offline due to “load shedding” as the city tried to protect the fragile system from overloading. That number is in addition to the 20,000 customers still without power in the Etobicoke area. At the peak of the storm about 300,000 customers were in the dark.

Customers in the following area are currently affected by the outage.

• St. Clair Avenue West south to Queen Street West and Howland Avenue to Parkside Drive

“As a result of a critical asset not being available during a real high demand day the rest of the system has been placed under real stress,” president and CEO of Toronto Hydro Anthony Haines said Tuesday. “That’s why we are asking people to reduce their use. We need to take that pressure off the backbone system until Hydro One has an opportunity to get into that station, assess the damage and restore it as necessary.”

Haines said in order to ensure the system has the capacity to handle demand, Torontonians need to collectively reduce their power usage by about 200 megawatts throughout the afternoon.

That amount equates to the electricity needed to power about 200 condominium buildings for a few hours.

“It is a big load, but it is not a catastrophic load,” Haines said. “It is absolutely in the realm of the doable with everybody’s help.”

Toronto Hydro sent out a message on Twitter asking customers to reduce their thermostats to 25 C during peak hours and then to shift back to 22 C during off-peak hours.

TTC Chair Karen Stintz also warned in a tweet that TTC service could be affected if hydro customers didn’t scale back on their usage today.

Ford wants review of emergency procedures

The rain began falling during the evening rush-hour Monday, flooding several roads and highways, including the Don Valley Parkway.

The downpour also submerged several stretches of GO Transit and TTC track, severely disrupting service and trapping about 1,400 passengers on one GO train near Bayview and Pottery roads.

In the wake of the chaos, Ford said he will be asking city manager Joe Pennachetti to review the city’s emergency response protocol and make recommendations on how the city can better respond to weather-related emergencies.

“Last night was unprecedented and I am extremely proud of our hard working staff who worked tirelessly through the night to restore services and ensure the safety of our residents,” Ford said. “There are many things that worked well last night, but unfortunately there are some areas that need improvement. Communication is a big one, but when there is a blackout it is hard."

Pennachetti said he was pleased with the city response to the flooding, but noted that there continues to be work do on the infrastructure front.

“We have issues in terms of some of our infrastructure, water, sewer, key areas, where we have to do our best to ensure that the backups are there,” he said.

The cost of the cleanup has not yet been determined, but it is expected to be significant.

Ford is expected to tour some of the harder hit areas from the storm later this afternoon.

"I am going first-hand so I can see the severity of the damage and Mr. Pennachetti will be working as quick as he can with the heads of the departments to get something for next week for sure," Ford said.

TTC service largely restored

The TTC shut down subway service completely on Monday night and was forced to reroute several streetcars and buses due to localized flooding.

By Tuesday morning, service had been largely restored, however there continues to be no service between Jane and Kipling stations on the Bloor-Danforth line due to flooding. Shuttle buses are running as a result.

“It was a fantastic effort by my staff. They performed a herculean task in getting everything back with the help of other agencies and I pay tribute to them for doing that,” TTC CEO Andy Byford said Tuesday. “They worked very intently on a prioritized and methodical basis to get everyone home safely and to get the service back up running today.”

GO train service continues to be affected by the flooding with a number of delays and service suspensions in effect. For a full list follow this link.

Remember for instant breaking news follow @cp24 on Twitter.