Lightning and slippery conditions have hampered firefighters battling three out-of-control bushfires in the Blue Mountains.
The NSW bushfire emergency is entering its seventh day and there are 59 fires burning across the state, with 18 uncontained.
Four out-of-control fires, three in the Blue Mountains and one at Balmoral in the southern highlands, are at the second highest alert level of watch and act.
The RFS is expecting severe and extreme fire danger throughout the day, with high temperatures and strong winds forecast for large swathes of the state, including the firezones as well as Greater Sydney and the Hunter.
Firefighters had been hoping to get the upper hand on the major blazes at Lithgow, Mt Victoria and Springwood overnight, but RFS spokesman Andrew Luke told AAP today that the bad weather has hampered efforts.
"We've had rain only as little as two to three millimetres received on the firegrounds, and that's hampered our efforts to backburn," said Mr Luke at RFS headquarters in Sydney.
"It's also meant we've had to remove crews from fire trails because of slippery conditions and to make sure we're not damaging those fire trails.
"What otherwise would have been good news has actually hampered us overnight."
He said there had also been "significant lightning activity" right across NSW from the central west to the southern tablelands and in the Blue Mountains, but it was too early to say if it had sparked new blazes.
Mr Luke says early weather forecasts indicate the high fire danger conditions predicted for Wednesday will eventuate.
"There's been no change to that," he said.
He said around 700 firefighters had been out battling blazes overnight.