Easing conditions over the weekend have allowed firefighters to strengthen containment lines around the North Black Range bushfire burning near Braidwood.
However, crews are preparing for deteriorating conditions later on Monday and Tuesday, driven by westerly winds and temperatures in the high 30s.
The fire remains at advice level and has burnt more than 35,000 hectares.
The northern part of the fireground, burning near Jones Road and Watsons Road, remains the most active.
The fire is active in the Warri and Manar area to the south of Manar Road and Butmaroo Road; in Harold Cross, north of Vernelly Road and Gumms Road; and in Buttmaroo to the south-east of Buttmaroo Road and Ingledow Road.
Hot spots continue to pop up near the centre of the fire and around the perimeter.
NSW Rural Fire Service Lake Gorge District officer Darren Marks said those hot spots had the potential to worsen under erratic conditions forecast for Monday afternoon and into Tuesday.
"Crews are mopping up and actively extinguishing those hot spots but they do have the potential for causing issues as the fires rage and conditions deteriorate," Mr Marks said.
"Monday is going to be challenging as the temperatures and the winds start getting up.
"Tuesday looks drier and hotter and that's a bigger issue."
More than 140 firefighters are battling the blaze, which has forced the closure of Araluen Road between Braidwood and Moruya.
NSW traffic authorities say residents along the road may be allowed access at the discretion of fire crews.
The Kings Highway has also been closed between Braidwood and Nelligen.
NSW Rural Fire Service spokesman Greg Allan said containment lines would be strengthened along large stretches of the fireground before conditions worsened.
"If a new fire starts up, it would spread very quickly," Mr Allan said.
"We'll be seeing those westerly winds tomorrow and higher temperatures could see a change in direction for the fire, which could see an elevation of fire activity."
Mr Marks said the fireground was experiencing a mix of inland and coastal weather patterns, which was making conditions hard to predict.
"We're expecting erratic behaviour and there's the potential for the fire to spread in any direction," he said.
He said the backburning efforts over the weekend had allowed fire crews to be prepared ahead of a challenging week ahead.
The Bureau of Meteorology said a high of 38 degrees was forecast for Tuesday with westerly winds throughout the day before a easterly change in the evening.
Temperatures are expected to remain in the 30s for much of the week.