Extreme fire danger and total fire bans are in place in large parts of the state while firefighters continue to battle the 28,000 hectare Willi Willi blaze west of Kempsey and another fire at Wise Creek east of Hat Head.
Properties are not currently threatened, but the hot, dry and windy conditions could see the fires break through containment lines, Rural Fire Service Deputy Commissioner Peter McKechnie warned.
"Both of those fires have been really challenging for firefighters right through the week," he told ABC News on Sunday morning.
"Quite challenging conditions for firefighters on the ground today and still a lot of fire actually on the ground.Â
"So people shouldn't be complacent that there hasn't been any threat for a couple of days. Today will be another challenging day."
Total fire bans are in place in the Greater Sydney region, the Greater Hunter, Northern Slopes, North West and the North Coast.
Mr McKechnie urged people to be prepared.
"Right through today, we will see fires in other areas I'm sure, and people need to know what they're going to do," he said.
With dry conditions forecast for some time, Mr McKechnie said regular fire activity is likely to continue throughout "a very long and challenging fire season".
Firefighters are still working to bring the Willi Willi fire, which last week destroyed seven homes, under control.
Last week 56-year-old Richard Mainey was killed defending his Temagog property from the fire.
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