Westerly winds of 55 to 80 km/h are forecast to impact the fireground this afternoon and in the worst case, a breakout could reach the forested areas of Braidwood.

At 1pm on Monday, the NSW Rural Fire Service had the fire at advice level and as "being controlled". The fire was more than 20,000 hectares in size.

People in the areas of Forbes Creek, Mount Elrington Road, Jembaicumbene creek, Bombay, Bendoura/Wallaces Gap Road, Majors Creek and Reidsdale were advised to activate their bush fire survival plan.

If that plan was to leave, they are to do so towards Braidwood.

Mount Elrington Road was identified as being at particular risk this afternoon, NSW RFS Lake George district officer Darren Marks said.

"The fire is burning to the north-west of Mount Elrington Road, winds could push fire and embers into Mount Elrington," he said.

An evacuation centre in Braidwood at the National Theatre at 100 Wallace Street will open at 2pm.

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Braidwood is forecast to reach a top of 16 degrees on Monday, according to the Bureau of Meteorology. Mr Marks said the cold weather had helped ease the impact of the fire.

"If we were having these winds on a 30 degree day, the fire would already be at the coast," he said.

About 100 firefighters are battling the blaze and are supported by bulldozers, graders and helicopters that are working to establish containment and protect properties around the fire.

Despite cooler conditions, the Currowan Fire on the South Coast remained at emergency level.

Mr Marks said the two firefronts were about 30 kilometres from each other and crews were working to contain the North Black Range fire at Cooma Road and the Currowan fire at Mongarlowe.

But he said if containment operations were unsuccessful there was a chance the two could meet up.

"It would absolutely cut the Kings Highway and you would be looking at a fire in excess of 100,000 hectares," he said.

Conditions are expected to ease through the week.

"We are expecting the winds to drop and in particular we will have good conditions in the evening for back burning and to create strong containment lines," said Mr Marks.

"But we're at the beginning of summer, we are experiencing erratic fire behaviour, there are no guarantees."