About 45,000 homes in Sydney's eastern suburbs lost power at the peak of the city's heatwave thanks to overgrown weeds.
Homes and businesses in suburbs including Double Bay, Edgecliff and Bondi Junction lost power at 11.26am, forcing shops to close, disrupting council services and leaving hospitals relying on backup generators for essential services.
The blackout was caused by overgrown weeds, believed to be shoulder-high in some places, that grew around the equipment in an electrical substation on the corner of Epping and Manning roads in Double Bay.
These weeds came into contact with the 132-kilovolt power cable where it emerges from the ground to connect to the switching equipment in Double Bay.
A spokeswoman for Prince of Wales said the hospital's backup generator kicked in immediately so no essential services were affected.
A number of people were trapped in lifts during the ordeal.
A mother and her eight-month-old baby had to be rescued from a lift in Kensington, while five people in Bondi Junction also had to be freed.
Shops including Aldi and Coles at Eastgate Bondi Junction were forced to close for an hour when retail systems went down.
Temperatures have soared in Sydney, with the Bureau of Meteorology updating its Thursday forecast to predict it would reach tops of 40 degrees in the west and the city.
During the blackout, just before midday on Thursday, it was 32.9 degrees at Observatory Hill, 31.1 degrees on Sydney Harbour and 35.2 degrees at Sydney Airport.