A storm cell bringing high winds and lightning is heading for the Blue Mountains, adding to the danger for firefighters battling out-of-control blazes in the area.
Rural Fire Service Commissioner Shane Fitzsimmons said the storm cell was headed from Bathurst towards Blackheath and was expected to hit around lunchtime (AEDT) on Tuesday.
He says the storm will probably only bring up to two millimetres of rain, but also lightning and strong winds, increasing the fire danger.
Winds of up to 70km/h had been detected.
"We're tracking a fairly active storm cell, near Bathurst headed towards the back end of the Blue Mountains," he told reporters at RFS headquarters in Sydney.
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"It's tracking towards the Blackheath area where they're doing that very critically important back burning."
Mr Fitzsimmons said the storm translated to "very difficult, very dangerous fire behaviour and firefighting conditions".
Firefighters in the field, particularly in the more rugged country, had been warned to be ready for the storm.
The RFS would look at "extracting" firefighters from the area if needed.
With around 24 hours before the worst of the forecast fire danger conditions developed in NSW, fire crews have seized the opportunity to take a more aggressive approach to back burning.
On Tuesday, they linked two of the Blue Mountains fires before they joined in more dangerous circumstance.
