HUNDREDS OF THOUSANDS of people sweltering through a brutal heatwave in southern Australia were left without power today, as the grid struggled with surging demand.

Authorities said more than 200,000 customers were experiencing blackouts after it ordered forced outages to reduce the risk of the entire grid failing.

“We have asked for 100 megawatts of involuntary load reduction, we have notified the networks, they’re in the process of doing that,” Australian Energy Market Operator chief executive Audrey Zibelman told reporters.

The disruption comes as temperatures in Melbourne soared to 42.8 Celsius just after lunch, before a cool change saw the mercury drop 12 degrees in just seven minutes in the city in the early afternoon.

There were reports of up to 100 traffic lights without power in Melbourne, and some shops and cafes were forced to close.

The extreme heat did not deter tennis fans however, who flocked to Melbourne park for the Australian Open tennis semi-finals — although many did make use of mist tunnels and fans to keep cool.

In other parts of Victoria state authorities had issued fire warnings — with hundreds of emergency services personnel and dozens of planes and helicopters on standby — as temperatures in some areas were expected to reach up to 47 Celsius.

Australia is reeling from a heat wave that peaked in South Australia Thursday when the state capital Adelaide topped 47.7 Celsius, breaking a record that had stood since 1939.

Meanwhile, authorities further south on the island state of Tasmania continued to battle bushfires.

- © AFP 2019.