The utility said equipment had failed, likely due to heat, causing an outage bounded by Kingston Road, Galloway Road and Guildwood Parkway at about 3:20 p.m. All power had been restored by 6:30 p.m.
The new outage came after 6,500 customers in Toronto's eastern downtown went without power for several hours on Thursday night and early Friday morning, after a circuit breaker overheated. The utility says the equipment sometimes overheats during a string of hot days because it isn't cooling down at night.
Hydro officials have been asking people to conserve electricity during the hot weather by turning down the air conditioning by a few degrees.
Environment Canada said the temperature hit 36.3 C at Pearson airport, eclipsing the 1998 record of 34.7 C. It was one of 11 records that fell in Ontario.
"When you get this kind of heat everybody’s reaction is to just crank up the air conditioning," CBC meteorologist Michelle Leslie said. "That really puts a strain on the power grid.”
An extreme heat alert that was declared by the city's medical officer of health on Wednesday still stands. During the alert, residents are advised to check on family, friends and neighbours, particularly adults and seniors at greater risk of suffering from heat-related illness.
The extreme heat alert also means city cooling centres are open for people who need them — and pool hours will be extended at many city-run swimming pools.
Temperatures will drop a little over the weekend as thunderstorms move in on Saturday. The high on Sunday is forecast to be 26 C.
But at least a few people will be missing the heat when it goes.
"I love it. I love the heat. Although it makes me sweat a lot I still enjoy coming outside because it's just so nice. And you know how everyone is always waiting for summer? Well it's finally here," said Pauline Salazar.
"I'm loving it and I think that it's beautiful and I hope it continues. I find the heat very nice — and I hope we don't have a winter." said Ralph Meranti.