Australian fires: 'Perfect storm' destroys 28 homes

In this photo provided by the New South Wales Rural Fire Service a fire burns near Sussex Inlet, Australia. Photo / AP

A "perfect storm'' of a fire in northern NSW has destroyed 28 homes, with firefighters expecting that number to rise.

The fire has burned through 40,000 hectares near the Warrumbungle National Park.

After Sunday's destructive rampage it remained uncontained on Monday, with a 100km front, although no further properties were immediately under threat.

But Rural Fire Service (RFS) Deputy Commissioner Rob Rogers told reporters that the number of homes destroyed was expected to go up as crews inspected burnt-through areas.

He said 40 farm sheds had also been lost along with many livestock, much fencing and farm machinery.

"There was just absolutely no stopping that fire,'' Mr Rogers said.

He said the wind shifted to the south at the worst possible time, creating "perfect storm'' conditions for a fire that burnt "with such a ferocity we haven't seen in years''.

Mr Rogers said evacuations were absolutely necessary and police had enforced that.

Mr Rogers said firefighters knew people who lost homes were hurting, but he urged them to be patient until it was deemed safe for them to return to their properties.

He urged everyone in a bushfire-prone area to prepare a bushfire survival plan.

"When you're full of adrenalin you do not make good decisions,'' he said.

Mr Rogers said he continued to be concerned about the fire danger in the entire northeast quadrant of NSW, apart from coastal areas that had received recent rain.

Mr Stoner said an assessment of damage costs had not been done, but "at the very least'' it would be hundreds of millions of dollars.

"The speed in which it developed and moved was absolutely frightening and I had genuine fear for people's lives,'' Mr Rogers said.

Acting Premier Andrew Stoner said NSW had been through "a hell of a week with bushfires'' and it was not over yet.

He said that while a wind change had removed the threat to the town of Coonabarabran, it could threaten settlements to the north of the national park.

Mr Stoner said it was "miraculous'' that the main building and telescope at the Siding Spring Observatory were not destroyed though the Australian National University facility was damaged in the fire.

He paid tribute to "heroic'' firefighters who prevented any loss of human life in the fire.

Around 170 fires remain burning across the state, with nearly 40 of them uncontained.

Mr Rogers said the Warrumbungle fire was believed to have been started by lightning, along with about 100 other fires in NSW on the weekend.

He said the plume from the fire went 14km into the air and embers were being blown 5km ahead of the fire front.

It would be some time before firefighters contained the fire so many evacuees, including those who lost homes, were not being allowed back in at this stage, Mr Rogers said.

- AAP