Australia battles bushfires across NSW as heatwave continues

Properties have been damaged or destroyed and at least one person has been treated for burns as almost 100 fires burn across the Australian state of New South Wales.

More than 30 of those fires were uncontained on Sunday night, with the Rural Fire Service issuing emergency warnings for four blazes near Port Macquarie, Dunedoo, Mudgee and Kempsey.

Fire Service commissioner Shane Fitzsimmons said hundreds of firefighters were battling the fires out of a pool of about 2500.

"This is the worst day we've seen in the history of NSW when it comes to fire danger ratings and fire danger conditions," Fitzsimmons said.

Dozens of properties could be under threat near Port Macquarie and Dunedoo, Fitzsimmons said, and there may have been one home lost in Boggabri.

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"At this stage, we have got some unconfirmed reports of homes being lost, sheds being lost and machinery being lost, and other agricultural assets being lost on some of these fire grounds," he said.

One firefighter was treated for burns and others sustained minor injuries, deputy RFS commissioner Rob Rogers told the ABC on Sunday night.

A southerly change on Sunday evening would present new challenges, Fitzsimmons said, with firefighters expected to have hours of work ahead of them.

"When a southerly comes in, what is typically the benign flank of the fire becomes a 10, 20, 30 km new fire front," he said.

"It's extremely volatile, we see increased wind strengths, we see very erratic and dangerous fire behaviour, we see spotting activity going in all sorts of directions."

However, conditions will improve for firefighters after the southerly passes the mid north coast fires.

There's the potential for damaging winds "but the good news is it should be all easing off by the early hours of Monday", Bureau of Meteorology senior forecaster Neil Fraser told AAP.

The bureau isn't expecting storms overnight and while the fire danger will remain very high on Monday in the Greater Hunter and surrounding fire areas, no part of the state will face severe, extreme or catastrophic conditions.

ARRESTS MADE

Three people have been arrested and charged with lighting fires acropss NSW.

 Fitzsimmons slammed the alleged fire bugs - males aged 13, 32 and 40 - for the "heinous crimes".

"How dare they," he told reporters in Sydney in Sunday.

"You put the lives of our firefighters at risk. How dare anybody add to the extraordinary conditions we're experiencing."

A 32-year-old man was arrested on Sunday afternoon after two fires were deliberately lit at Nabiac on the NSW north coast.

Earlier, a 40-year-old man was arrested on the Central Coast after fire crews were called to a blaze in Mango Creek.

A 13-year-old boy was arrested on Saturday afternoon after he allegedly started a grass fire in Orange that prompted the evacuation of an animal shelter.

A witness told officers they saw the 13-year-old, who was part of a group of teenagers, light a grass patch in an industrial area of Orange on Saturday evening.

The group fled, but the boy was later taken to the Orange police station and charged with destroying property, setting fire to the property of another and failing to comply with direction of the minister.

HIGH TEMPERATURES NOT HELPING

A heat wave on Australia's east coast saw temperatures hit records in some parts of the state, creating conditions that officials said were worse than those preceding Victoria's 2009 "Black Saturday" fires, Australia's worst bush fire event that killed 173 people.

Temperatures climbed above 45 degrees Celsius in some parts. Dry and hot northwesterly winds coming from Australia's desert centre, some up to 75 kilometres an hour, were fanning the bushfires.

A southerly wind change associated with a cold front was forecast to arrive by early evening, the Bureau of Meteorology said.

Fitzsimmons said the front would eventually offer relief, but would create volatile conditions as it met the northwesterly flow.

Since Friday, heat wave conditions caused cancellation of major sporting events and put pressure on the electricity grid.

A paper mill, water treatment operations and Australia's largest aluminum smelter, Tomago, were among businesses halting operations to conserve energy on Friday.

- Syndey Morning Herald, AAP