"Catastrophic fire danger ratings are the worst conditions that we can experience when it comes to fire danger ratings".
"We are likely to see broad areas under Severe and Extreme fire danger ratings".
The Rural Fire Service has also warned of a potential "catastrophic" fire danger warning on Sunday largely around the Hunter, from the coast, mid-north coast, out through the Central Tablelands, the top end of the greater Sydney region and out to the central west.
Lower Hunter RFS zone manager Superintendent Jayson McKellar said the region's 90 RFS fire trucks and their crews were ready for any action, along with several helicopters already at Cessnock to help attack any threats as soon as they arrive.
NSW Rural Fire Service Commissioner Shane Fitzsimmons described the conditions as being "as bad as it gets", telling Fairfax Media that the forecast was "without precedent in NSW". To hammer the point home, he said "it's not another summer's day". It's not another bad fire weather day.
About 300 firefighters were on the ground and thousands more were on stand-by.
Fleabag star set for Chewbacca-style role in Han Solo spin-off film
Actress and writer Phoebe Waller-Bridge is reportedly set to star in the forthcoming Han Solo spin-off film. She was nominated for a Critics Choice Television Award for Best Actress in a Comedy Series.
The Fire Service warns the fire risk could reach catastrophic levels across the state and stay there for several hours.
"The Bureau of Meteorology is forecasting a significant heat wave event across many parts of NSW over the weekend, with temperatures exceeding 40 degrees in some locations".
The conditions may spark fears of a repeat of "Black Saturday" in 2009, when soaring temperatures and high winds fanned the flames of a series of bushfires across the state of Victoria.
He said any fire that started in catastrophic conditions would be "extremely hard to control".
The states of New South Wales and Queensland have felt sweltering temperatures, exceeding 40C, in recent days.