At least 13 bushfires raged across NSW yesterday, an elderly woman died in a house fire and another woman jumped from a second-floor balcony to save her life after separate blazes destroyed four homes.

Beaches were packed as people tried to beat the heat while others sought out air-conditioned movie theatres and shopping centres.

At least three people were taken to hospitals with heat exhaustion.

Lifesavers were busy with surf rescues, treating people with heat complaints. And a man had his hand mangled in an apparent shark attack at Surf Beach, near Batemans Bay, about 4.30pm.

Temperatures hit 40.1 degrees in the Sydney CBD and a high of 42.4 at Olympic Park in the west.

The mercury also broke the 40 mark in Bankstown, Richmond and Penrith, before a southerly change that dropped temperatures about 10 degrees about 6.30pm.

A Parramatta resident recorded 47 degrees on her veranda while shoppers reported that four stores in the inner-west had sold out of portable air-conditioners.

But the cooling wind also brought problems, with trees and power lines brought down across the metropolitan area.

"We're receiving calls about once every two minutes," fire brigades spokesman Ian Krimmer said.

A total fire ban was imposed across most of the state.

At 4pm demand for electricity in NSW reached 12,622 megawatts, near the all-time high for this summer of 13,581 megawatts, according to National Electricity Market Management Company.

"That high was set on a weekday when demand is higher because businesses are running and there's a lot more load on the network," corporate communications general manager Paul Bird said.

Bruna Pene died in a house fire in Steward Street at Hammondville, in Sydney's south-west, about 1.30am yesterday.

"The fire was just too fierce," a neighbour said.

Two hours later, a woman escaped with minor injuries when she jumped from the second floor of a burning block of units at Maryville, in Newcastle.