Aggressive firefighting strategy seems to be yielding "positive results" in the raging inferno that have enveloped Blue Mountains of New South Wales (NSW). The NSW Rural Fire Service (RFS) had started backburning in an effort to contain the spread of the fire front.

With hotter and windier weather conditions predicted for Wednesday, NSW firefighters, on Tuesday morning managed to merge two out-of-control fires as they attempted to stop the danger of a three front "mega-fire." The two out-of-control fires that the NSW RFS successfully merged are the one at Lithgow and Mt Victoria.

Speaking to reports in Sydney, RFS Commissioner Shane Fitzsimmons said the strategy had helped them make progress.

"We are seeing positive results of these very deliberate, very targeted, very decisive strategies being deployed particularly in relation to backburning operations," he told reporters.

"We have made a significant inroad into just how far these fires are likely to advance over the next 24 and 48 hours," Mr Fitzsimmons said.

"I just don't know how far they're going to run yet...but what we do know is that together we have done everything we can to stop them getting as far as Richmond and the outskirts of Western Sydney," he said.

NSW Emergency Minister Mike Gallacher welcomed the positive signs resulting from the aggressive firefighting effort.

"The firefighters in the field have actually confronted the fire threat to the Blue Mountains rather than waiting for that threat to come to Sydney," Mr Gallacher said.

"Whilst it is promising, we should not be complacent. This fire is still alive. It's still a risk," he added.

Weather conditions, meanwhile, is expected to deteriorate further on Wednesday.

Tuesday, however, saw some rain forecast for the fire grounds.

As a result of its intense effort, and the light rain over the fire zone, the RFS has meanwhile downgraded the State Mine fire near Lithgow, from "emergency" to "watch and act" status.

Briefing reporters on the firefighting effort, RFS spokesman Ben Shepherd, said although the immediate threat to properties in the Lithgow vicinity had eased, residents were being warned not to get complacent.

"It (the warning level) will probably go up again, but the immediate threat to a number of those properties has definitely eased," he is reported to have told AAP news agency.