The NSW Rural Fire Service (RFS) has warned Tuesday's bushfire risk for the Greater Sydney and Greater Hunter areas is set to be "catastrophic".

It is the first time the Sydney region has been rated at that level since the new fire danger ratings were introduced in 2009.

The RFS has issued a strong warning that "lives and homes will be at risk" as high temperatures, strong winds and low humidity combine to create fierce conditions.

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It has advised people in areas at risk to head to larger towns, shopping centres or facilities away from bushland areas.

Schools in high risk areas will also be closed on Monday and Tuesday.

The NSW Department of Education has issued a list of more than 40 schools closed on Monday.

Elsewhere, danger warnings at "extreme" level are in place for Tuesday for the North Coast, Illawrra and Shoalhaven, Central Rangers, Northern Slopes and the north-western area.

Danger in the Far North Coast, New England, Far South Coast, Southern Ranges and Lower Central West Plains has been rated as "severe".

A statewide total fire ban is in place for Monday and Tuesday.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 51 seconds 51 s A number of properties on the NSW Mid North Coast were destroyed

Meanwhile, two firefighters have been injured after a burnt tree fell onto a fire truck at Nambucca Heads on the mid-north coast on Sunday.

The firefighters were battling to contain the Kian Road fire, south-west of Bowraville.

One of the firefighters was stepping out of the truck when the tree fell and she was knocked to the ground.

A fire truck was hit by falling branches at Nambucca Heads on Sunday, injuring two firefighters. ( Supplied: NSW RFS )

The woman sustained neck and spinal injuries and was airlifted to John Hunter Hospital.

The second firefighter was sitting in the back of the truck.

He suffered neck injuries and was taken to Coffs Harbour Hospital.

Devastating fires raged through the state on Friday and Saturday, destroying more than 150 homes and killing three people in conditions described as "apocalyptic".



Temperatures dipped to single figures in some areas overnight on Saturday, giving fire crews a much-needed reprieve.

Emergency alerts were issued on Sunday afternoon as winds picked up for the blazes affecting Johns River, south of Port Macquarie, and Mt Nardi National Park near Lismore, but were later downgraded.

More than 60 fires continued to burn on Sunday night.

But the wider focus is now on preparations for the week ahead.

The RFS issued a dire warning for Tuesday, saying: "If you are threatened by fire, you may not get help."

RFS Commissioner Shane Fitzsimmons said: "Indications are that the weather conditions will be worse than what we experienced [on Friday]."

"Not only will they be worse, they will be concentrated much further than just the north-eastern area of NSW."

Mr Fitzsimmons said along with the 1,300 firefighters on the ground right now from across Australia and New Zealand, they were in contact with colleagues from Canada and the US for possible help in light of Tuesday's predicted forecast.

They were also in discussions with the Australian Defence Force.

Prime Minister Scott Morrison was touring the fire ground on Sunday and spoke to some of those affected at an evacuation centre at Club Taree.

Scott Morrison with 85-year-old Owen Whalan at the Club Taree evacuation centre on Sunday. ( AAP: Darren Pateman )

Brooke and Tristan Smith tend to their home at Wallabi Point, near Taree. ( AAP: Darren Pateman )

He said he was "never more proud" of Australians than in moments like this.

"They just show incredible spirit, incredible heart, incredible generosity," he said.

He said there was an immediate disaster recovery payment available of $1,000 for adults and $400 for children affected by the fire.

The Prime Minister was joined by NSW Premier Gladys Berejiklian, who thanked the thousands of volunteers across the state. She said the conditions for Tuesday looked "dire".

Authorities have warned residents across the state should begin preparations now — once the bushfires break out, resources may be too stretched to help them.

A 'quality person'

The warnings come as two more victims killed during Friday's extreme fire event were identified as George Nole and Julie Fletcher.

Ms Fletcher died at Johns River, north of Taree.

Her neighbour Russell Souter told the ABC she was a "quality person" from a well-known family in the area.

"Her family has been in the area for generations and own quite a bit of land," he said.

"It is just a tragedy."

Mr Nole died at the Kangawalla fire ground near Glen Innes.

He was described as "true gentleman" who taught the town's young people about electronics and photography.

The third fire victim, 69-year-old Vivian Chaplain, had been trying to protect her home at Wytaliba.

More than 150 homes have been destroyed in NSW since the fire emergency began on Friday.

However, that number is expected to rise.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 3 minutes 3 seconds 3 m 3 s Nymboida residents survey the damage

Dean Sgarbossa from the Bureau of Meteorology said sea breezes were expected to blow through several fire grounds on Sunday.

"When it's combined with dry atmosphere conditions and high temperatures but particularly stronger winds, that leads to very intense fires but also very rapidly-moving fires," he said.