Sydney has awoken to a thick blanket of smoke as NSW 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.

Hot and dry conditions and a lack of rain means the smoke is likely to linger.

The density of the smoke in the city has been deemed poor, meaning it poses a risk to people with heart or lung conditions.

“Everyone, especially people with heart or lung disease should avoid outdoor exertion and stay inside as much as possible,” the environment department advises.

“If you have symptoms rest and use your reliever medicine. If symptoms persist, seek medical advice.”

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.

On Monday night there were 51 grass and bush fires burning around NSW, all at “advice” level, with 28 yet to be contained, the RFS posted on Twitter.

“More than 1300 firefighters continue work on these fires tonight, ahead of forecast hot, dry and windy conditions tomorrow,” the agency said.

Tuesday and Thursday will be “tough days”, Rural Fire Service Deputy Commissioner Rob Rogers told reporters in Sydney on Monday.

source 7news.com.au

Todays morning commute… Sydney covered in smoke haze! Expecting a top of 37c 🔥 pic.twitter.com/Ipj2gFIp4W

— Suganthy (@SugntyRam) November 18, 2019

This is the smoke over Sydney this morning. I drove over the Harbour Bridge to work and you could barely see from one side to the other. This is from a fire 200+km away. It’s not even summer. #NSWBushfires #ClimateEmergency pic.twitter.com/ME0yTQsomr

— Freya Noble (@freyanoble) November 18, 2019