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Sydney has awoken to a thick blanket of smoke as New South Wales residents are urged to "stay vigilant" amid severe fire dangers and a hot, windy weather forecast.
Most of NSW's east coast is under severe or very high fire danger ratings on Tuesday as almost 50 blazes burn across the state, with more than half of those uncontained.
"It's fair to say all of these fires have got the potential to present real challenges today," Rural Fire Service NSW Chief Commissioner Shane Fitzsimmons said on Tuesday.
Weather conditions will pose problems for the 1400 firefighters on the ground battling flames fanned and spread in different directions by "really problematic" gusts reaching up to 65km/h.
"Not only have we got these high temperatures, the mid to high 30s, dry atmosphere, we've got this real mix of converging winds," he told ABC News.
Winds dragged smoke from a fire at Gospers Mountain - northwest of Sydney - over the city on Tuesday morning, and the haze from the 140,000-hectare fire isn't likely to dissipate until a southerly afternoon change.
The central Sydney air quality rating is poor and people with asthma or other breathing issues are being warned to stay indoors, avoid outdoor exercise and seek medical advice as needed.
In Sydney's northwest, air quality has been deemed hazardous.
Following weeks of difficult bushfire conditions and last week's 'catastrophic" warnings, Mr Fitzsimmons said it was crucial people didn't take anything for granted.
"The last thing we want is lethargy or complacency or fatigue to set in when it comes to monitoring these conditions," he said.
Six lives and 530 homes have been lost since the NSW bushfire season hit some weeks ago, with more than 420 homes destroyed in the past fortnight alone.
Parts of the state under severe fire danger on Tuesday are Greater Sydney, Greater Hunter, Illawarra-Shoalhaven, Southern Ranges and Central Ranges fire regions.
These regions, along with the Northern Slopes and North Western regions, are also under a total fire ban.
Much of the rest of eastern NSW is under very high fire danger.
Some 1.6 million hectares of land have been lost so far - more than the entire 1993/1994 bushfire season.
Emergency Services Minister David Elliott on Monday said the biggest risk this week would be firefighters becoming fatigued.
A DC10 air tanker has been drafted in from North America to help drop up to 38,000 litres of water and retardant on blazes and efforts will be bolstered by help from New Zealand firefighters, Mr Elliott said.