Most of NSW's east coast is under severe or very high fire danger as the state heads into the first of two "tough days" for the week with temperatures likely to rise into the 40s and little-to-no rainfall forecast.
Six lives and 530 homes have been lost since the state's bushfire season hit some weeks ago, with more than 420 homes destroyed in the past fortnight alone.
Last night there were 51 grass and bush fires burning around NSW, all at "advice" level, with 28 yet to be contained, the RFS posted on Twitter.
"More than 1300 firefighters continue work on these fires tonight, ahead of forecast hot, dry and windy conditions tomorrow," the agency said.
Tuesday and Thursday will be "tough days", Rural Fire Service Deputy Commissioner Rob Rogers told reporters in Sydney on Monday.
Parts of the state are under severe fire danger today including Greater Sydney, Greater Hunter, Illawarra/Shoalhaven, Southern Ranges and Central Ranges fire regions.
These regions, along with the Northern Slopes and North Western regions, are also under a total fire ban.
Much of the rest of eastern NSW and the ACT is under very high fire danger.
Mr Rogers said some 1.6 million hectares of land have been lost so far - more land loss than the entire 1993/1994 season.
Firefighters were on Monday battling a firefront of some 6000 kilometres, the equivalent distance of a return Sydney-Perth trip, he said.
Mr Rogers said firefighters were "singularly focused" on preventing further loss of life and property and warned people to stay alert.
"Even though it's not a catastrophic danger (this week) it's still going to be bad fire days," he said.
He urged anyone who had not yet been affected by bushfires to "please use this as a wake-up call", warning them to take steps including cleaning out gutters and having a fire safety plan in place.
Premier Gladys Berejiklian asked everyone to "maintain their vigilance".
Emergency Services Minister David Elliott said the biggest risk in the coming days would be firefighters becoming fatigued.
A DC10 air tanker had been drafted in from North America to help drop up to 38,000 litres of water and retardant on blazes and efforts will be bolstered by help from New Zealand firefighters, he said.