Australia has issued 'catastrophic' alerts after record-breaking temperatures and wild lightning storms sparked more than 100 fires across the country, officials said yesterday.

Unseasonably hot and dry weather combined with strong winds to fan scores of blazes in the country's southeastern states, many of which were sparked by overnight lightning strikes.

"It has never been this hot, dry or windy in combination in November ever before," said New South Wales (NSW) state premier Nathan Rees.

A massive fire was threatening around 100 homes in the NSW town of Rylstone, west of Sydney, and residents were warned to evacuate or prepare to fight the flames, the Rural Fire Service (RFS) said.

Three homes were razed last Friday night at the beachside town of Dolphin Sands in Tasmania, Australia's southernmost state. There were also smaller outbreaks in South Australia and Victoria states, but conditions there had eased.

Across New South Wales five major blazes were raging out of control and RFS Commissioner Shane Fitzsimmons said crews were racing against time to contain the flames ahead of a forecast worsening in conditions. Lightning without rain was expected to hammer the state overnight before the mercury soars above 40˚C today, accompanied by high winds, the weather bureau said.

"It is a very tenuous situation with these unprecedented conditions," Fitzsimmons said.

"We are expecting strong northwesterly winds to reach the Sydney basin, and temperatures could reach the low 40s," RFS spokesman Ben Shepherd added.

"With strong winds, the fires could reach homes... It will be very dangerous fire weather."

More than one-third of NSW was under a Code Red or Catastrophic fire alert, in which residents cannot be forcibly evacuated but are strongly advised to abandon their property due to extreme risk of death or injury.

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