Some 45,000 homes across Sydney's eastern suburbs have been hit by power outages amid a heatwave in the coastal city in southeastern Australia, with media reports of residents being trapped in lifts and one hospital losing electricity.

Distribution company Ausgrid said on Thursday that emergency crews were investigating the cause of the widespread outage, which is uncommon in Sydney's upmarket beachside neighbourhoods.

Power was lost to homes and businesses in suburbs from beachfront Bondi to the well-heeled areas of Double Bay and Woollahra.

Authorities warned drivers to take care as dozens of traffic lights had been blacked out.

Ausgrid, which provides power to more than over 1.7 million customers down the east coast, later said power had been restored to 10,000 homes around Double Bay.

Australia's bureau of meteorology on Thursday warned hot dry weather could persist to the end of April, with a 70 percent chance the majority of the country would experience above-average temperatures.

A record-breaking heatwave across southeastern Australia earlier this month triggered outages in some areas and sent power prices soaring, while bushfires have destroyed homes in the southern island state of Tasmania.

Last week, Adelaide, in the country's south-central coast, hit a sweltering 46.6 degrees Celsius, creating a new temperature record and becoming Australia's hottest city in the process.