Buildings lost in North Black Range fire in Tallaganda National Park near Braidwood east of Canberra

Erratic conditions and fire spotting proved a challenge on Saturday, and those conditions are not expected to let up on Sunday.

NSW Rural Fire Service spokesman Richard Thorek said the fire would not likely be contained until Monday.

"Firefighters were challenged by strong winds however they managed to prevent the fire spread beyond our main containment lines, particularly beyond Cooma Road. A little fire did cross Cooma Road but only got about 500 metres or so," Mr Thorek said.

"The firefighters did some really good work to contain the erratic and unexpected fire today," he said.

He said some firefighters had received minor injuries in the line of duty, and others had suffered from illnesses related to heat and exhaustion.

A hand-built home in Bombay, near Braidwood, was destroyed by fire on Friday night. Another property at Carwoola was destroyed in a fire on Saturday night, in an incident unrelated to the North Black Range bushfire.

Conditions eased slightly on Saturday night but residents are still being urged to remain vigilant.

An easterly wind change brought a slight relief to firefighters on Saturday evening. Crews were expecting to conduct backburning operations to help strengthen line breaks during the night.

At 10.30pm, the fire was downgraded to alert level and was being controlled.

Mr Thorek said the easterly wind blowing across the fireground meant people in Forbes Creek and Hoskinstown should expect to see some increased fire activity, but the fire on that side of the national park was within containment lines.

The wind would also mean a smoky evening for residents in Carwoola, Queanbeyan and Canberra.

He said the southern side of the firefront was the most concerning, in the region of Jembaicumbene.

"If it breaks containment tomorrow that area and Majors Creek are our areas of concern."

The fire has now burnt more than 20,000 hectares in Tallaganda National Park and surrounds near Braidwood since it was ignited by lightning on Tuesday.

Residents in the vicinity of the fire who are not physically and mentally prepared to defend their properties are being asked to leave early while the path out is clear.

The fire is considered as "being controlled" when there is a plan in place to contain the blaze. That plan was able to be enacted on Saturday morning when conditions had eased.

The Kings Highway has been reopened after earlier road closures but some localised closures continue to remain in place.

A total of 24 firefighting trucks and 90 personnel were be on the ground on Saturday. Three water-bombing helicopters were also helping tackle the blaze in the morning but were grounded by high winds in the afternoon. Four dozers and three graders were putting in containment lines on Saturday morning.

The ACT Rural Fire Service deployed five trucks and 23 personnel to the fire on Friday and eight trucks, 35 people and two command vehicles on Saturday.

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Bureau of Meteorology senior forecaster Jake Phillips said warm temperatures on Sunday combined with wind would make firefighting conditions difficult.

Sunday is expected to be another dry day with dusty westerly winds sweeping through the area. Temperatures are predicted to drop below average on Monday to a maximum of 15 degrees.

Mr Phillips said Canberrans would see some smoke in the city on Sunday morning, while those near Braidwood could expect smoke to linger over the weekend.

ACT Health advises people with respiratory or heart conditions to stay inside and limit physical activity.