Some Victorians could be without power for hours as more than 48,000 homes struggle with no electricity as a heatwave continues to grip the state.

Temperatures have soared to over 45C, sending homes into blackouts across the afternoon, with numbers peaking from 6pm.

The outage stretches to the Mornington Peninsula and Geelong.

The Bellarine Peninsula is one of the hardest hit, with more than 15,000 homes in beachside towns down, the Herald Sun reports.

People have had to use candles as they struggle with no power across most of Sunday evening because if Victoria's heatwave

Many have taken to social media calling for more to be done on their power being restored. Some towns have reached temperatures of 45C

Customers east of Melbourne could be waiting longer and those in Geelong might be waiting until the morning.

Spectators at the Australian Open men's final on Sunday night have also had to endure a stick game as Melbourne sweats through the back end of an unbearably hot Australia Day long weekend.

'(It will be) extremely uncomfortable conditions, particularly on Sunday night,' Weatherzone forecaster Stuart Coombs told the ABC.

'You don't really get the chance to recover after the 39 degrees very well so it does make it very stressful on the body.'

Temperatures soared about 40C on Sunday evening, causing more than 48,000 people to lose power and 15,000 spectators to sweat through the Australian Open men's final

Fuse faults, the extreme heat and increased demand are to blame for the power outage.

Walpeup had the highest temperature in Victoria at 5.25pm with 45.7C.

Conditions will remain unseasonally humid until late Monday, Bureau of Meteorology forecaster Dean Stewart said.

'It's unusual that you'll have high temperatures combined with the very high humidity,' he told AAP.

Towns without power stretch across the state, with the Bellarine Peninsula one of the hardest hit

'It doesn't often get this humid when you've got temperatures around 40C.'

Australian Open officials have confirmed they will review the extreme heat policy at the end of the tournament after a number of players made complaints.

Serbia's Novak Djokovic said the conditions were on the verge of being unplayable and France's Gaels Monfils said he felt like he was dying on court.

France's Alize Cornet needed treatment after lying down on the court in her defeat by Elise Mertens.

People will get a reprieve from the hot and sticky conditions with a cool change expected to hit Melbourne on mid-Monday afternoon, BoM says.