Firefighters will battle a bushfire, burning in national parkland amid severe fire conditions, into the night in the NSW Hunter Valley.
The Rural Fire Service issued an emergency warning after 5pm on Wednesday for the bushfire in the Wollemi National Park and Putty State Forest.
People on Bakers and Putty Valley roads were advised to take shelter and were warned "it is too late to leave" as strong westerly winds whipped up the fire.
The fire was downgraded to Watch and Act level about 9.30pm but homes remain under threat.
Firefighters are remaining on scene as embers blow ahead of the bushfire, creating spot fires which may impact homes before the main blaze.
The blaze has burned more than 2400 hectares and residents at Cessnock have been warned of smoke and ash in the area.
"The fire is generating a large column of smoke that is blowing all the way towards Cessnock," the RFS told media earlier.
At Muswellbrook, a grass fire near the Golden Highway at Hollydeen was brought under control late in the afternoon.
Total fire bans are in place in nine regions of NSW including Greater Sydney, Greater Hunter, the Central Ranges, Illawarra/Shoalhaven, New England, North Western, Northern Slopes, Southern Ranges and the Southern Slopes.
Temperatures are expected to reach 41C in Moree and Walgett in northern NSW and Muswellbrook in the Hunter region on Thursday.
Penrith in Sydney's west and Tibooburra in the state's far northwest are forecast to reach almost 40C.