A total fire ban is in place across most of New South Wales as hot, dry and windy conditions return.
The Rural Fire Service (RFS) has imposed a ban that stretches from the Illawarra to the far north coast and inland to the Central Ranges, New England and the Upper Western districts.
A severe fire danger rating is also in place for those areas.
RFS spokesman Brendan Doyle says temperatures in some areas will reach the high 30s.
"Winds are gusting up to 70 kilometres an hour and there is fairly dry air as it moves through, so the relative humidity is quite low," he said.
"Fires can start quite easily and spread quite quickly. Not only [are] firefighters going to be vigilant, but we're asking people themselves to be vigilant.
"Report any new fires immediately because under these weather conditions, minutes can matter."
Mr Doyle says firefighters have been back-burning to strengthen containment lines.
"Strike teams are being arranged to be on standby if any other new outbreaks take off," he said.
'No moisture across the state'
Meteorologist Mick Logan says a southerly change in the afternoon will not bring much relief.
"We just have no moisture across the state at the moment, we really need some rain across a lot of these fire grounds but this is a dry change," he said.
Temperatures will drop to around 20 degrees Celsius by Monday.
NSW fire investigators are also examining the source of two fires that began early this morning in the lower Blue Mountains.
A crime scene has been established at Glenbrook around two hectares between Surveyor Abbot Drive and Mitchells Pass that caught fire at about 1:00am (AEDT).
The RFS says blacking out is continuing as fire investigators work to establish the cause of the blaze.
Hazardous smoke pollution
Authorities say there's hazardous smoke pollution across parts of Sydney, as fire crews continue to fight bushfires that are yet to be contained.
The Environment Protection Authority says there are hazardous pollution levels in Sydney's east and north-west.
A particle pollution alert is in place for the Illawarra, south of Sydney.
The Rural Fire Service's Ben Shepherd says the smoke is being caused by back-burning which is being done to help contain existing bushfires.
"We are actually setting fire from containment lines in an effort to contain these fires especially that one in the Hawkesbury," he said.
"So we have actually had to set fire to the ground in an effort to stop it moving continuously in an easterly direction.
"If we were to let it go, it would potentially push all the way to places like the northern parts of Sydney or even the central coast."
© ABC 2013
15:20 EDT Farmers in Western Australia's Wheatbelt have borne the brunt of a hailstorm that swept through the region at the weekend.