New South Wales’ bushfire crisis has arrived in Sydney, with two massive blazes threatening homes on two sides of the city.

A total fire ban has been declared for areas surrounding the Harbour City on Saturday as a deteriorating weather forecast has weary authorities on high alert.

Several suburbs in the south-west were under threat Friday as windy conditions blew embers ahead of a fire front in Wollondilly.

Meanwhile, several blazes combined north of Sydney Friday morning to create a 60km “mega fire” stretching all the way to Singleton, on the banks of the Hunter River.

Strong winds fanned the flames towards several suburbs in south-west Sydney, were Oakdale man Luke Wright helped save his brother’s home.

“It’s been going on all day, a fire came from the back and we put it out,” he said.

“But then another one came from the side so the fireys covered the house in foam.

“The fence has been damaged but that’s about it, very lucky.”

Oakdale man Luke Wright has a breather after helping to save his brother’s home. Photo: ABC

So far this season, 684 homes have been destroyed by bushfires in NSW.

The temperature in Sydney’s CBD is expected to hit 26 degrees on Saturday, but closer to the firegrounds at Camden in the south-west there is a forecast high of 34 degrees.

Bureau of Meteorology forecaster Dean Sgarbossa said while Saturday was expected to be difficult for firefighters, there was good news on the horizon.

“Although we will see a continuation of dry, hot conditions, the winds will ease,” he said.

“Some will ease on Saturday but more so on Sunday when the pressure builds over the Tasman Sea, directing lower temperatures, high humidity but lighter winds, particularly over the adjacent coast where many of these fires are located.”

At 5:30, there are 94 bush and grass fires burning across NSW. 11 fires remain at Watch and Act alert level where there has been an ongoing threat to properties overnight. Severe fire danger forecast for New England and Northern Slopes. #nswrfs #ALERT pic.twitter.com/Mp19YqjCQW

— NSW RFS (@NSWRFS) December 6, 2019

The smoke that has shrouded Sydney on-and-off for weeks is not going anywhere, however.

Mr Sgarbossa said it would “stagnate” over the Sydney basin and surrounding areas today, before easterly winds tomorrow blow it further inland.

The Bureau warned “some fires were too big to put out” and the level of smoke was such that it was showing up on its radar as rain.

ABC weatherman Graham Creed pointed out that if “85 per cent of NSW population lives within 50 kilometres of the coast, that means 6.8 million people are under some level of threat of direct impact or health issues related to bushfires”.

A total fire ban is in place for seven regions on Saturday including Greater Sydney.

The updated totals came as the blazes burning north-west of Sydney joined to create what has been dubbed a “mega blaze” on Friday morning.

The Gospers Mountain fire in the Hawkesbury region merged with two fires in the Lower Hunter – the Little L Complex blaze and the Paddock Run fire near Singleton.

The three fires have burned through more than 300,000 hectares and destroyed about 10 homes.

This video shows the dangers of embers being blown ahead of some of the large fires burning across NSW. This is the Green Wattle bush fire burning near Lake Burragorang. The fire is impacting on the area around Nattai.#nswrfs #nswfires pic.twitter.com/92n2ymWbS5

— NSW RFS (@NSWRFS) December 6, 2019

NSW Premier Gladys Berejiklian has urged residents to remain vigilant.

“We have seen the fire is coming to very close proximity to major population centres, whether it is on the South Coast, Central Coast, or even Greater Western Sydney,” Ms Berejiklian said from the RFS control room in Sydney.

“We know there have been some property losses, the extent of which won’t be known until the fire conditions are safe for people to go in and have a look, but we also appreciate that many families and many people have been asked to leave their homes and we can appreciate what a scary time this is for many people.”

Ms Berejiklian has repeatedly said now is not the time to talk about the impact of climate change on bushfires.

But according to a UNSW community survey released on Friday, 53 per cent of respondents say it is right to talk about global warming during extreme events.

Just 35 per cent of Australians surveyed said it’s not OK.

Almost the entire coastal area of NSW and much of the state’s north-east is under a severe fire danger rating, while total fire bans are in place for the southern ranges, Illawarra-Shoalhaven, Central Ranges, Greater Sydney, Greater Hunter, Northern Slopes and northwestern regions.

-ABC