NSW firefighters are taking advantage of cooler conditions to tackle blazes burning across more than 2.2 million hectares but they've been warned warmer weather will return next week.
More than 2000 firies were out battling 100-plus bush and grass fires on Friday as cooler temperatures helped crews work to contain some bushfires.
The NSW Rural Fire Service said conditions are expected to worsen next week.
Maximum temperatures are forecast to reach the high 30s or early 40s in areas including Dubbo, Orange, Mudgee, Moree, Bourke, Parkes and Penrith.
Authorities have warned people to remain vigilant about their health as air quality remains poor in parts of Sydney and it may worsen again in coming days.
A poor air quality alert has been issued for Sydney on Saturday.
NSW Health's Dr Richard Broome said the city's air quality had improved in recent days but people still needed to monitor the conditions and take action when smoke returned.
"People with heart and lung conditions, young children and pregnant women may be more sensitive to smoke," Dr Broome said in a statement on Friday.
"I'd urge these groups to avoid vigorous outdoor activity on smoky days."
For the fourth straight week, emergency departments presentations and calls for ambulance assistance over asthma or breathing problems have been higher than normal.
Between December 5 to 11, there were 1357 relevant emergency department presentations compared to the five-year average of 916.
There were 2448 ambulance calls for breathing problems compared to the five-year average of 1742.
Dr Broome said that while smoke might cause no more than eye or throat irritation for most people, the numbers showed those with known respiratory conditions needed to be cautious.
The fire danger will be very high in several parts on NSW on Saturday, including the central ranges, Greater Hunter, northwest, southern ranges and northern slopes.
The RFS confirmed this week that 724 homes, 49 facilities and 1582 outbuildings had been destroyed so far this fire season. Six people have died and 2.7 million hectares have been scorched.
Australian Associated Press