Firefighters in eastern Australia have been assessing damage from ferocious wildfires that have devastated communities and are rushing to prepare for "bad, if not worse" conditions expected to flare in the coming days.

Catastrophic fires have killed three people and destroyed more than 150 homes since Friday, but cooler weather overnight provided a measure of reprieve for firefighters and residents.

More than 100 fires are still burning across New South Wales and Queensland, including dozens of blazes that remained out of control.

Five people reported missing have now been found, but the unpredictable nature of the disaster means officials have not ruled out the possibility that others could still be missing, said NSW Rural Fire Service spokesman Greg Allan.

The mayor of the small town of Glen Innes, where two people died, said residents had been left traumatised and were still coming to terms with their losses.

Carol Sparks said the fire was as high as 6m and raging with 80km/h winds.

"It was absolutely horrific for the people that were impacted (by) it."

In Old Bar, which was spared the worst when the wind changed direction, hectares of bushland had turned into charcoal and small pockets of flames continued to smoulder.

Peter McKellar, 75, was clearing debris from his property as his neighbour's home sat in ruins.

"The firies (firefighters) saved ours," he said. "They are doing a wonderful job. They're angels."

High temperatures, low humidity and strong winds forecast from the middle of the week are predicted to fuel blazes that authorities have warned they will be unable to contain ahead of time.

The remains of a property destroyed by fire in Bobin, 350km north of Sydney

"Under these conditions, these fires will spread quickly and will threaten homes and lives," the NSW Rural Fire Service said in a statement.

"These conditions will be as bad, if not worse, than those experienced on Friday as they will be across a much broader area including large population centres like Sydney."

In Queensland, more than 1,200 firefighters are battling 51 active fires across the state, with 39 aircraft deployed to assist for the first time ever in the state.

"Queensland does not usually have a fire season like we've experienced this year and last year," Premier Annastacia Palaszczuk told reporters.

With thousands of people forced to flee from their homes, Australia's government was offering immediate emergency assistance payments of up to Aus$1,000 to those affected.

Firefighters have been praised for their bravery and help

Bushfires are common in Australia but the country has experienced a dramatic start to what scientists predict will be a tough fire season - with climate change and weather cycles contributing to the dangerous combination of strong winds, high temperatures and dry conditions.

The current disaster has not wreaked the human devastation of Australia's worst recent bushfires, the Black Saturday fires that killed 173 people in Victoria state in 2009, with some experts attributing that to better early warning systems.

But Ross Bradstock, from the Centre for Environmental Management of Bushfires at the University of Wollongong, described the situation as "unprecedented" for the affected regions, which have rarely - if ever - experienced such severe fires.

"Sadly, given the weather forecast for the coming week, the crisis may worsen and extend southward into landscapes primed to burn via extreme dryness," he said.