An evacuation order has been issued for the Kosciuszko National Park and resorts within the area.
The park itself is closed to visitors but people living within the boundaries have been told to get out by 10 am on Friday.
The Rural Fire Service said it feared that prevailing winds could move the fire eastwards which would take it closer to the Namadgi National Park and Canberra.
Guests in Thredbo were preparing to leave on Thursday afternoon. "We are under planned evacuation at the moment," a worker at one business said.
"A lot of people have left. The whole planned evacuation means that everybody stays calm," she said. "The guests that are still here understand that they have to get ready to leave."
But it was not clear that everybody was leaving. On Thursday afternoon, the receptionist at the Thredbo Alpine Hotel couldn't say whether they would leave.
A series of fires were active in a strip stretching south for about 100 kilometres to the west of the park.
The Rural Fire Service said that this Dunns Road fire was burning in the Jingellic area to the east of Albury. There were fears for other areas as conditions looked like worsening dramatically on Saturday.
The Rural Fire Service was to hold public meetings at 11 am on Friday to "provide the latest information on bush fires within the Snowy Monaro local government area".
The venues were:
- Adaminaby School of Arts Building (Memorial Hall)
- Bombala RSL Club
- Cooma's Centennial Park Bandshell
- Jindabyne Memorial Hall
The mayor of Snowy Valleys Council, James Hayes, urged residents who don't need to be in the region impacted by fire to leave.
"If you've got somewhere you can go - friends you can visit - get there," he said.
The Mannus Correctional Centre near Tumbarumba was to be evacuated, according to Corrective Services NSW.
Extra staff were being brought in to help with the evacuation, with all 155 minimum security inmates going to Junee Correctional Centre.
Assistant Commissioner Custodial Kevin Corcoran said in a statement: "The safety of our staff and inmates is paramount when deciding whether to evacuate a correctional centre."
Wednesday's national parks statement said: "All people located in Kosciuszko National Park must exit Kosciuszko National Park boundaries before the deadline of 10am Friday."
"This is an essential measure to protect life. "This is not a fire season that NSW has seen before. It is hotter and drier than we have previously experienced."
This is not a fire season that NSW has seen before. It is hotter and drier than we have previously experienced.National Parks statement
The township of Tumbarumba and the region around it were on high alert, with warnings that two nearby fires converge into a mega-blaze on Saturday.
Witnesses said there was a "scene of devastation between Batlow and Tumbarumba".
The RFS was advising residents to enact their fire plans.
Landholders were warned to prepare for worsening conditions on Saturday.
The NSW Department of Primary Industries and the Local Land Services urged landholders in the region to activate their bush fire survival plan and to consider moving livestock off site.
Conditions are forecast to worsen on Saturday on the fire ground.