Sydney - At least 30 homes have been lost to forest fires in Australia's south-east as high winds and record-breaking temperatures combine to create tinder-box conditions.

Two people are in hospital with serious burns after trying to save homes from blazes on the outskirts of Melbourne.

Australia's second-largest city recorded is hottest February day, with the temperature above 44 degrees Celsius. Officials warned of a possible repeat of the blazes in
1983 that left 75 people dead.

"The fire intensity is such that none of our tactics will have any effect at all on the headfire in most situations," said deputy fire chief Greg Anof. "So it's really a matter of asset protection, of houses where you can, of trying to pick up flanks where the fire behaviour might be a bit more moderate, but a day like today, it's just impossible."

A blaze burning out of control in the Bunyip National Park north of Melbourne blackened more than 2,000 hectares and razed homes, a golf club and farm buildings.

A reporter for national broadcaster ABC who was flown over the fire in a water-bombing helicopter described what she saw.

"It's impossible to see if there are houses and properties gone because the smoke is so dense and black and widespread that you just can't get a helicopter in there to see it," she said.

Paul Bird, from the company that operates the electricity grid, warned that the fires could knock out power to over 100,000 Melbourne homes.

"It does look at this stage, unless the situation improves, we may lose well over 100,000 customers and possibly many more than that," Bird said.

The south east has roasted in record temperatures for a fortnight. Sydney broke an all-time record of three consecutive days of plus-40-degree-Celsius heat and Adelaide had its highest temperature on record.

To thwart arsonists - half of forest fires are believed to be deliberately lit - authorities have closed some national parks and put under surveillance those they suspect of being firebugs.

In what may have been a first, a court last week refused a volunteer fireman bail because of fears he couldn't resist re-offending in such perfect conditions. Charged with setting forest fires that he later helped put out, he will go to trial next week.

In Adelaide 10,000 volunteer firefighters and 11 water-bombing aircraft were being marshaled to tackle forest blazes.

In the north-east corner of the continent the emergency services are dealing with the worst flooding in decades. More than 60 per cent of Queensland - 1 million square kilometres - is affected and dozens of houses have been lost.

Because roads are cut and delivering feed by helicopter is impracticable, tens of thousands of stranded cattle are being left to die.

Yet another day of rain has stoked fears that the cattle-farming town of Ingham will have to be evacuated.

"That's the concern we have and if that happens we're in for a massive disaster," Ingham Mayor Pino Giandomenico said. (dpa)