'Difficult season': bushfire warning as homes destroyed

Devastating bushfires are giving Australians a taste of what authorities believe could be a long and dangerous summer.

About 76 bush and grass fires were still burning in NSW on Sunday morning, including more than 20 yet to be contained.

An out-of-control bushfire destroyed at least 12 homes in Koolewong on Saturday, not far from built-up areas on the Central Coast.

Another four homes were lost at Bulahdelah on the Mid North Coast.

NSW Premier Chris Minns travelled to the bushfire-hit area on Sunday, speaking to families who had lost their homes in the lead-up to Christmas.

"They were prepared for this to happen and they were able to get as much as they possibly could in the car and evacuate in a short space of time," he told reporters at Gosford RSL Club.

The RSL was set up as an emergency evacuation centre and "inundated" with phone calls from locals wanting to donate food, toiletries, nappies and, in some cases, their homes as crisis accommodation, Mr Minns said.

Federal and state disaster assistance funding has also been activated across the Central Coast, Mid Coast, Upper Hunter, Muswellbrook, Warrumbungle and Dubbo.

The declaration will allow residents, businesses, primary producers and councils to lodge claims for immediate cash and recovery loans.

More than 250 firefighters, 50 trucks and nine aircraft were battling the Koolewong blaze at its peak.

Several firefighters experienced heat exhaustion and there were reports of minor injuries to civilians.

Other properties and outbuildings were damaged beyond the 12 homes lost, with confirmation of the extent of the devastation expected later on Sunday.

NSW Police investigators and the Rural Fire Service are working simultaneously to determine the cause of the blaze, which started at the back of properties on Nimbin Rd.

A cool change was threatening to complicate efforts on Sunday morning, producing wind speeds of 40km/h.

"This is an example of what we might see through the upcoming summer season," RFS Commissioner Trent Curtin said.

"The fire here yesterday in Koolewong jumped a kilometre spread for an ember that moved into the Woy Woy bay area."

The Bureau of Meteorology told NSW emergency service heads last week to brace for a very challenging bushfire season as a result of hot winds and a warmer Pacific Ocean in December, Mr Minns said.

"We can't set in stone what summer will look like," he said.

"Because of uncertain weather predictions, it's incredibly important you expect the unexpected.

"Have a bushfire preparedness plan in place and be ready to leave, maybe even at the drop of a hat."

Prime Minister Anthony Albanese and Federal Emergency Minister Kristy McBain received a briefing on the fire situation in Canberra on Sunday.

The fires in NSW, at Dolphin Sands on Tasmania's east coast and in Western Australia's Kimberley region foreshadowed a "difficult season", Mr Albanese said.

"NSW, in particular, has a range of pre-conditions if you like for being quite a difficult one," Mr Albanese told ABC's Insiders.

Mr Curtin said a fire at Milsons Gully had burned more than 11,000 hectares and remained a concern, along with another at Redhead, south of Newcastle, that prompted an initial emergency warning early on Sunday.

Temperatures are expected to ease from Sunday for most of NSW and southern Australia, though the heat will build across northern Australia and WA and return to much of the country early in the week.

"We've got a reprieve over the rest of this week to bring many of those fires to contained," Mr Curtin said.

"But we all need to know fires will continue to start, whether that's from lightning or from other activities, this summer."