Homes at Wentworth Falls could be threatened by an out of control bushfire within hours, the Rural Fire Service (RFS) said on Saturday morning.
More than 100 firefighters are working on the blaze in an inaccessible area near the Upper Mountains town.
"The fire is out of control and is expected to impact on homes in the next few hours," the RFS stated at 6.45am.
"The fire is burning in the area of Hordern Road, Coronation Road and Tableland Road. Access to the fire is difficult as it is burning in an inaccessible area and has dropped over the cliff escarpment.
"Fire activity has increased over the past few hours due to strengthening winds. It is expected that these winds will remain strong for most of the day and this will hamper efforts in controlling the fire.
"Further NSW RFS crews will be sent this morning and they will be assisted by a number of waterbombing helicopters across the day."
The RFS has advised residents to be aware of burning embers which may start spot fires ahead of the main fire front.
"If your plan is to leave, or if you are not prepared, consider leaving to family and friends away from the fire affected area," the RFS stated.
An emergency alert text message has been sent to homes in the area.