Firefighters say immaculate planning and cooperation from the public helped prevent a potentially catastrophic bushfire emergency in NSW as temperatures soared on Thursday.

But they've warned against complacency with conditions expected to deteriorate again on Sunday.

Just after 3pm (AEDT) on Thursday, Sydney reached 37.3 degrees, making it the third hottest October day in 154 years.

The top temperature in NSW was recorded at Wilcannia in the northwest, where it reached 42 degrees.

Gusty winds coupled with the hot conditions created extreme fire danger for southern parts of the state, including Sydney, the Hunter, Illawarra and Shoalhaven, and forced a total fire ban in most of NSW.

There were thousands of firefighters and volunteer crews on stand-by along with 80 Rural Fire Service aircraft.

At times throughout the day fire crews were dealing with 60 fires burning across the state, including 30 uncontained blazes.

But only a handful of fires reached the "watch and act" fire alert level.

"It's a result of the public adhering to warnings but also calling in fires when they saw them, and having crews on stand-by and flooding them with resources when we needed them," Inspector Ben Shepherd of the NSW Rural Fire Service told AAP.

He said crews were spending Friday containing some of the fires still burning, including one burning out of control at Morrows Road in Nana Glen in the Clarence Valley, in anticipation of Sunday.

The Bureau of Meteorology predicts maximum temperatures of 30C and above in Sydney, the Hunter, Central Coast and Illawarra regions.

"Sunday will be the next worrying day," he said.

Meanwhile, two teenagers were charged on Thursday and Friday with lighting a fire in bushland at Windale that started a blaze at a reserve on October 2.

The boys, aged 13 and 14, will appear in children's court on October 21.

 

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