ACT ESA commissioner Georgeina Whelan advised that on Monday there was one bushfire burning within the ACT, the Hospital Hill fire in the southern remote area of Namadgi National Park.

The fire, believed to have been ignited by lightning, was less than one kilometre in size and was being controlled, Ms Whelan said. It was 34 kilometres from the closest residential suburb and posed no threat to properties.

"It is a small fire that is controllable under our current weather conditions," she said.

"We have ACT firefighters and heavy plant [machinery] on the ground, working to extinguish the fire, which is now fully surrounded by our firefighters, and to build containment lines."

Two strike teams at the fire had managed to build six kilometres of containment lines within the ACT border and were working with the NSW RFS to work on containment lines outside the territory.

A helicopter had water-bombed the area and the ACT's special intelligence gathering helicopter would continue monitoring the fire and fires in NSW.

She said crews would monitor the Hospital Hill fire for the next 72 hours. The expectation was it would be extinguished in that time, but crews would remain on site to ensure it posed no risk.

"The tactics we're applying to that and the level of resourcing we're applying to that, my aim would be to have it extinguished as soon as possible," Ms Whelan said.

"I don't want that fire still going on Friday."

Conditions are expected to deteriorate on Friday and a total fire ban was likely.

Ms Whelan reminded the community of the need for them to be bushfire ready because in the case of an emergency bushfire in the territory, it would not be possible to have crews everywhere.

"My aim is that the fires do not get anywhere near our residents. But in the event that they do we need you to be bushfire ready," she said.