The number of homes confirmed destroyed this bushfire season in NSW has risen to more than 600, the Rural Fire Service says, as firefighters battle some 50 blazes still burning across the state.
As more hot, dry and windy conditions led to severe fire danger ratings on Thursday and blanketed much of Sydney in a smoky haze, the RFS revealed a total of 612 homes have been lost to date.
The fires have also claimed six lives this bushfire season.
In the past fortnight 503 homes have been destroyed and 178 damaged while more than 1300 outbuildings have been damaged or destroyed, the RFS said. Almost 8000 buildings have been saved.
A thick haze also covered Sydney and the NSW coast on Thursday morning as a northeasterly breeze dragged smoke towards the city.
People with chronic respiratory or heart conditions were warned to stay indoors.
"If you do develop symptoms and they don't get better with your normal reliever medication you should seek medical advice and in an emergency you should call triple zero," Dr Richard Broome, director of environmental health at NSW Ministry of Health, said.
The air quality across much of Sydney was hazardous for visibility on Thursday, NSW environment department readings showed.
The RFS said smoke is being mixed with dust from the state's west.
The haze and poor air quality over the city is likely to last through the weekend as bushfire smoke from the north of the state is blown south, the Bureau of Meteorology said.
"The smoke will linger around. It will go off and come back again as the wind changes but we will see these smoke haze conditions for several days," forecaster Abrar Shabren told AAP.
Some 50 bushfires are still burning in NSW, 20 of which are uncontained. More than 1000 firefighters remain in the field.
There are 12 total fire bans in place across the state.
Several fires were upgraded to watch and act level on Thursday afternoon, including the 164,000-hectare blaze at Gospers Mountain northwest of Sydney and the out-of-control bushfire in Bora Ridge, south of Casino.
The RFS tweeted aerial footage showing smoke billowing into the air from the latter fire, which has now consumed more than 33,000 hectares.
There are also "watch and act" alerts in place for a pair of small fires west of Armidale at Abington and Camerons Creek and a fire west of Albury in southern NSW on the Riverina Highway at Coreen.
A severe fire danger rating is in place for 10 areas, including Illawarra-Shoalhaven. The entirety of the state's south is under "very high" or "severe" fire danger as hot winds blow in from South Australia.
Winds of up to 60km/h are forecast across the southern border region which could present challenges if there are new fires, Mr Fitzsimmons said.
"Another difficult day for firefighters, for people in these at-risk areas," RFS NSW Commissioner Shane Fitzsimmons told the Seven Network on Thursday.
But, after a fortnight of serious fires, he's hopeful conditions will soon improve.
"Hopefully, once we turn the corner on today there'll be an easing of conditions more broadly across the state," Mr Fitzsimmons said.
It's hoped northeasterly winds along the coast will help stop fires spreading and support firefighters in their bid to protect properties through backburning, which will continue on Thursday.
The RFS said dry lightning, something which could spark fires, is forecast for southwestern areas of the state with a southerly change on Thursday evening.
Australian Associated Press