Sydney  - Australia is to be the hottest place on the planet this weekend with temperatures set to breach 45 degrees in the south-east corner of the continent, officials warned Friday.

The big worry is that arsonists would take advantage of ideal conditions and lay potentially deadly forest fires.

"We're going to have unbelievably high temperatures, and we're also going to have unbelievably high winds," Victoria state Premier John Brumby said. "We've got a state which is just tinder-dry."

He warned of a possible repeat of the blazes of 1983 that left 75 people dead. Fire brigades are on high alert with all the state's fleet of water-bombing aircraft on standby.

Residents of Melbourne fear a repeat of the power blackout the heat wave has brought in recent weeks.

In neighbouring New South Wales, all 70,000 volunteer firefighters were to be on call. National parks where the danger of arson is high would be placed out-of-bounds to the public.

People were being asked to watch out for those deliberately lighting fires and to report any suspicious behaviour to police.

More than half of Australia's forest fires are believed to be the work of arsonists. (dpa)