The greater Sydney region will be under catastrophic fire danger on Tuesday for the first time since new fire ratings were introduced a decade ago, after a horror weekend which saw three people die in NSW bushfires.
More than 60 bush fires continued to burn across the state on Sunday night as conditions eased, with all of the blazes at "advice" and "watch and act" alert levels.
The RFS says catastrophic fire danger is forecast for the greater Sydney and greater Hunter regions - including the Blue Mountains and the Central Coast - for Tuesday due to worsening conditions.
"Catastrophic is as bad as it gets. Homes are simply not designed to withstand fire under those conditions," RFS spokesman Anthony Clark told ABC on Sunday.
"We've got big population centres covered by that catastrophic fire danger - but also up on the north coast where we've simply got a lot of fires burning at the moment, those fires have got a real potential to run and impact on lives and properties.
"So the risk is very real."
It is the first time since new fire danger ratings were introduced in 2009 that catastrophic fire danger has been forecast for Sydney.
Large areas of the state are also predicted to see severe and extreme fire danger.
Schools in identified high risk areas will be closed and the RFS advises those in the areas of catastrophic fire danger to avoid bushfire-prone areas.
More than 40 schools in NSW will also be closed on Monday due to the impact of the fires in the state's north.
Parents, carers and staff should not put themselves at risk by travelling if in doubt about whether their school will be open, the department said.
Education Minister Sarah Mitchell said students sitting their HSC should contact their school if unsure if exams will occur, or if it is unsafe for them to get to an examination venue.
"Students unable to attend an examination due to the bushfires will not be disadvantaged," she said in a statement.
A statewide total fire ban has been issued for Monday and Tuesday.
Of the 60-plus bush and grass fires still burning on Sunday night, just under half were not yet under control.
"We're simply not going to contain many of those fires before the bad conditions do hit on Tuesday," Mr Clark told ABC.
With authorities still to complete a detailed assessment of damage done from the weekend's blazes so far, the RFS says at least 150 homes had been destroyed.
RFS spokesman Greg Allan said a lot of the areas facing extreme fire danger risk on Tuesday have higher populations than the areas that have suffered fires so far.
He urged people to monitor conditions over the next two days and use the time to get ready and know what they will do if fire threatens.
"You need to take responsibility for your own safety," he told AAP.
Premier Gladys Berejiklian visited devastated bushfire communities on Sunday, telling reporters people were in a "traumatised" state.
"What really hit me today is even though some people know that their homes are OK they are still extremely traumatised by what they have experienced," she said.
The premier said the federal and state governments had already moved to put disaster relief arrangements in place.
The RFS will also coordinate relief work with the Australian Defence Force.
A woman who died as she tried to flee the weekend's devastating bushfires was identified by media on Sunday as Julie Fletcher, 63.
Ms Fletcher's body was discovered on Saturday night in a burnt-out home in the town of Johns River some 40km north of Taree on the mid-north coast.
Wytaliba residents Vivian Chaplain, 69, and George Nole were also named as victims.