Tens of thousands of Melbourne homes and businesses have lost power as air-conditioners combating temperatures of 44C taxed the power supply.
The city on the south coast of Australia was expected to see its hottest day since February 7 2009 – a day of catastrophic wildfires remembered as Black Saturday.
That day, the temperature soared to 46.4C, with wildfires killing 173 people and razing more than 2,000 homes in Victoria.
Scores of wildfires are raging in heatwave conditions across much of drought-parched south-east Australia, with authorities warning the fire risk is high.
Audrey Zibelman, chief executive of the Australian Energy Market Operator, which manages the national electricity grid, said three heat-stressed coal-fired generators had failed in Victoria and a fourth was expected to shut down on Friday.
The grid began loading-sharing as temperatures climbed in the early afternoon, with 30,000 households and businesses at a time being switched off for as long as two hours so supply could keep up with demand, Mr Zibelman said.
Essential services such as hospitals were quarantined.
Alcoa, the state’s largest power user, agreed to power down its aluminium smelter.
Several other businesses also agreed to wind down operations during the period of extraordinary demand.
Black Saturday had been the hottest day recorded by a major Australian city until Adelaide reached a searing 46.6C on Thursday.
The South Australia state capital of 1.3 million people — 400 miles west of Melbourne — beat its previous 80-year-old record of 46.1C set on January 12 1939, and records tumbled in smaller towns across the state.
The South Australian town of Port Augusta, with a population of 15,000, topped the state at 49.5C.
The Australian Open tennis tournament in Melbourne invoked its extreme-heat policy on Thursday and closed the main stadium’s roof during a women’s semi-final.
Bureau of Meteorology forecaster Rob Sharpe said he would not be surprised if this month becomes Australia’s hottest January on record with heatwave conditions likely to persist.