Dozens of Illawarra fire crews spent the weekend aiding a major backburning effort at the Green Wattle Creek bushfire in anticipation of dangerous weather conditions forecast for Tuesday.
Milder temperatures and winds on Sunday allowed crews from Albion Park, Farmborough Heights, Otford, Mt Keira, Dapto, Calderwood, Bulli, Gerringong, Mount Kembla and Helensburgh to help Southern Highlands crew conduct critical backburning around the Lake Burragorang fire.
The strategic burn comes ahead of an impending heatwave on Tuesday, which will see temperatures soar into the 40s across south-west Sydney, winds of up to 40km/hr in the early afternoon and possible lightning strikes.
In the Illawarra, Wollongong is forecast to hit 33 degrees, with similar wind strength.
Illawarra RFS district officer Matt Reeves said focus had now turned to the looming hot spell.
"Tuesday is looking like being another very difficult day," he said.
"People need to be preparing their properties, ensuring they clear away any bush fire fuels."
Mr Reeves said the current crop of fires across the state were moving rapidly and exhibiting erratic behaviour.
"The reactions times [for residents to decide to stay or go] is far less than what they ordinarily would be," he said.
Meanwhile, tankers from Jamberoo, Mount Keira, Darkes Forrest and Mt Kembla responded to a grass fire in the Cataract catchment area around 11am on Saturday.
Crews were able to contain the fire to a small area and extinguish it within a few hours.
Firefighters returned on Sunday morning to "mop up" the area, ensuring no trees or branches remained smoldering.
The cause of the fire is under investigation.
A short time later, a waterbomber helicopter believed to have been chartered from the Illawarra company crashed while assisting fighting a blaze north of Newcastle.
A Nine News video shows the chopper bearing the logo of Touchdown Helicopters, a privately owned charter company based at Shellharbour Airport in Albion Park Rail.
The pilot, who was the only person on board, was taken to John Hunter Hospital in Newcastle as a precaution.
On Saturday evening, tankers from Dunmore and the Illawarra support brigade drove south to Turmeil to help crews backburn at the Currowan fire, while Bawley Point residents were allowed to return to their homes on Sunday but warned to watch out for changing conditions.
As of Sunday evening, the Currowan fire remained at Advice level and the Green Wattle Creek fire was at Watch and Act.