The New South Wales Rural Fire Service says conditions are deteriorating across the state, with dry north-westerly winds forecast to return.

More than 37,000 hectares have now been burnt as 60 fires continue to burn across the state, 15 of them uncontained, and there is an active fire edge more than 300 kilometres long.

RFS commissioner Shane Fitzsimmons says new information from the Bureau of Meteorology this morning has firmed up concerns about the next few days.

"We are likely to see deteriorating conditions starting this afternoon as we've already been acutely aware of, but more so as we move into Monday and Tuesday," he said.

"The worst of that weather be probably culminating on Wednesday, but [there won't be] much relief in the intervening period."

Mr Fitzsimmons says drawing a parallel with the current emergencies with past fires would mean going as far back as the 60s, specifically a major fire in 1968.

"We've got what would be unparallel in terms of risk and exposure to the Blue Mountains throughout this week," he said.

"The reality is, however, these conditions that we're looking at are a whole new ball game and in a league of their own.

As weather conditions deteriorate, NSW Premier Barry O'Farrell says the situation may be worse than first thought.

"Whilst it is true that the weather on any day is never good at times like this, it's also clear that the weather forecast, the weather modelling, suggests the weather is not going to be as good as it had been previously anticipated," he said.

"Plans have been made, particularly around the three fires in and around the Blue Mountains, to introduce more coordinated management and control functions.

"Crews have been back-burning overnight to strengthen containment lines and are on alert to switch to active firefighting if properties come under threat."

Mr Fitzsimmons says Wednesday is predicted to be the worst day for fires.

"We've seen some extraordinary devastation and destruction already in recent days and there is very real potential for a whole lot more to come as we look down this week," he said.

"Right now, there is planning and decisions being made with a view to start broadcasting information and messages to large areas of the communities that are likely to come under threat throughout today, and planning and contingencies in place for those communities likely to come under threat in coming days."

Emergency warnings issued to Bell community for State Mine fire

An emergency warning has been issued for the State Mine fire, with residents of the Bell community urged to leave the area if unprepared.

Sorry, this video has expired Homes lost in Springwood and Winmalee

The NSW RFS says those leaving the area should travel west along the Bells Line of Road towards Lithgow, where the Lithgow Workers Club is open as an evacuation centre.

Residents in Kurrajong, Bowen Mountain and Yarramundi areas are being asked to use today to prepare their homes and monitor the fire situation.

A total fire ban has been declared for the Sydney, Illawarra, Hunter and Central Ranges areas.

Watch and act warnings remain in place for fires at Balmoral Village, Springwood, near Lithgow and Mt Victoria after fires flared again yesterday afternoon.

The fire between Lithgow and the Blue Mountains, west of Sydney, has crossed Tootie Creek and is heading towards Bilpin.

Fire crews have made use of the cooler temperatures overnight to back burn in and around the town.

In the Blue Mountains, fire has been spotted over Chifley Road at Bell and may impact the area.

Fires at Springwood and Mount Victoria are being controlled but there is still lots of smoke in those areas.

An uncontained fire has burnt through more than 12,500 hectares in the southern highlands and there is a potential threat to properties in the Wilson's Drive area, west of Bargo.

High temperatures are forecast later today and north-westerly winds are expected to cause fires to flare-up around the state.

"There was some earlier predictions of showers throughout Tuesday, Wednesday and Thursday but that prediction has backed off quite significantly," Rural Fire Service spokesman Kane Lambkin said.

"If anything does come out of it, it will just be a few smatterings of showers throughout New South Wales.

"It would take a significant amount of rain to moisten the ground enough to slow the progression of these fires.

"These fires will be running for many days if not weeks yet."

At least 200 homes already lost

Cooler conditions overnight did help the 1,500 firefighters undertaking back burning and strengthening containment lines.

This morning RFS spokesman Russell Taylor confirmed the loss of 208 homes since the fires started on Thursday, but he says that number is not final.

"There's more bushfire impact assessment people going to the field today," he said.

"They did the initial survey. They're going to go back today to make sure all of the correct boxes are ticked. With so many properties it's possible that somebody's ticked the wrong box, so we're going to double-check that today."

In the worst-hit parts of the Blue Mountains rows of homes have been destroyed in some streets.

At least 40 houses were destroyed on Buena Vista Road at Winmalee.

On Thursday, one man died trying to protect his home a fire that burnt from Doyalson to Catherine Hill Bay, at Lake Macquarie.