The number of properties damaged or destroyed by bushfires raging across NSW is set to rise after firefighters lost control of a backburn, inadvertently starting another blaze.
Up to 20 buildings - including homes - are feared lost after the backburning at part of the huge Gospers Mountain blaze northwest of Sydney spread out of control on Sunday.
The news comes as the Bushfire and Natural Hazards Cooperative Research Centre warned NSW faced a long and challenging fire season ahead after an unprecedented start.
With 2019 registering the second-hottest and driest January to November period for Australia, the centre warned the combination of severely dry conditions, high temperatures and low humidity was behind the dangerous fire season.
The entire eastern third of NSW is facing an above-normal fire potential into 2020.
Emergency warnings were issued on Monday for the Gospers Mountain blaze, the nearby 1600-hectare fire at Palmers Oaky and the Kerry Ridge fire in the state's Hunter region.
People living in the Wolgan Valley, Wallerawang, Lisdale and Blackmans Flat areas have been told it's too late to leave as the Gospers Mountain fire approaches.
Greenpeace issued a statement on Monday as the RFS warned of the fire approaching Wallerawang, which is close to the operating Springvale coal mine as well as an abandoned power station.
Greenpeace noted the town of Blackmans Flat was "immediately adjacent" to the Mount Piper Power Station which has large stockpiles of flammable coal.
"Obviously workers are at extreme risk as well as the community living nearby, as if any coal caught alight it would likely burn for weeks," communications manager Nelli Stevenson said.
The Gospers Mountain bushfire - which is nearing 400,000 hectares in size - was also upgraded to emergency level on Sunday when a controlled blaze started by firefighters breached containment lines.
The affected properties are thought to be in the Mount Wilson and Bilpin areas and might include some belonging to local RFS members.
RFS commissioner Shane Fitzsimmons said firefighters were trying their best to help the local community and had been "executing some very sensible, some very risky, some very challenging, decisions".
"Unfortunately things don't always go to plan and we've seen how quickly things can change and how destructive the consequences can be," he told ABC TV.
Some 450 customers are without electricity due to damaged power lines in the upper Blue Mountains, Endeavour Energy said on Monday.
The bushfire has also closed some roads in the area including the Bells Line of Road from Bilpin to Bell.
The Gospers Mountain fire now extends from the Lithgow area in the west, through the Hawkesbury area towards the Central Coast in the east.
Along with six adjoining blazes it's been dubbed a "mega-blaze" and has burned through more than half a million hectares.
Almost 2000 firefighters are battling 108 blazes across the state.
Total fire bans are in place on Tuesday for the northwestern and northern regions where the fire danger rating will be "very high".
The Bureau of Meteorology has forecast severe heatwave conditions for most of NSW throughout the week.
Ahead of the soaring temperatures, Western Sydney Local Health District on Monday warned residents to keep well hydrated and cool to avoid heat-related illnesses.
The public was asked to check in on elderly friends, neighbours and relatives.
Forested areas on and east of the Great Dividing Range will continue to see above-normal fire potential this summer due to forecast warmer and drier conditions across the state, the cooperative research centre said.
Areas to the west of the divide have reduced fire potential because the drought has left minimal grass.
Fire has already consumed almost three million hectares of land across the state this bushfire season driven by hot, dry and windy conditions.
Some 724 homes, 49 facilities and 1582 outbuildings have been destroyed while six people have died.