Police will allege they were searching bushland just off the Berowra Track about 8.30am on September 13 when they saw the man standing near a fire. They said he attempted to flee and was arrested.

Police will also claim the man, who will appear in Hornsby Local Court tomorrow, lit fires on September 5 and August 24.

In the Hunter Valley, an emergency warning was issued for the raging fire, which burnt almost 400 hectares, and broke its containment lines at Richmond Vale, near Kurri Kurri, about noon.

The volunteer-run Richmond Vale Rail Museum, founded in 1977, was guttered when the fire burnt along Leggett’s Drive but houses along the road were spared or saved.

Distraught museum chairman Peter Meddows put the damage bill at “at least $1 million”.

“It’s heartbreaking, there were 38 years of work, voluntary labour and personal money that went into it,” Mr Meddows said. “There’s a 100-year-old break van that’s just ashes now.

“It’s hard to think of what to do or what to say.”

A coal hopper built in 1880 was also totally destroyed. along with more than 1km of train track.

Students at Black Hill Primary School, 15km northeast of Richmond Vale, were evacuated as a precaution. The Rural Fire Service said that while the children were safe, they were taken to the nearby M1 freeway, where their parents collected them.

A Hercules C130 tanker, on loan from the US and capable of carrying 15,000 litres of water, was deployed to help crews fight the huge blaze, near Kurri Kurri.

The bushfire blazed as temperatures hit 35C in Sydney and the Hunter Valley, and the state was placed under numerous fire bans, with 75 blazes watched.

Bureau of Meteorology forecaster Elli Blandford said south Sydney recorded some of the hottest temperatures in the state, with Bankstown hitting 35C at 2pm and Sydney Airport hitting 35.3C at 2.15pm. Moree reached 34.8C, Port Macquarie was 34.8C and Kempsey had a high of 35.5C.

“In Cessnock and surrounds in the Hunter Valley, we have had pretty strong winds and high temps and it has been very dry, all of which contributes to having these bush fire prone conditions,” she said.

“Cessnock was 33.4 and we’ve had wind speeds around Cessnock up to 35km/h and gusts of up to 59km/h.”

By late afternoon, the emergency was declared over and the fire was downgraded to wait and act status.

However in the early afternoon, Andrew Mavin, a former firefighter with 27 years experience who lives close to the blaze, said the Richmond Vale fire was showing all the signs of trouble.

“There’s nothing to stop it. The smoke is turning the sun blood orange at the moment,” he said.

“It’s going to pose major problems all day. The thing that’s stacked against them (the firefighters) is that there is a southerly coming. When it hits, it will push the fire north and it’ll swap the lines and the flanks all around on you, it’s crazy,” he said.

A rural fire service spokesman said the fire was heading to houses on Leggett Drive, and there were crews and aircraft in that area fight it.

Properties on Orchard Rd, Whitebridge Rd and Richmond Vale Rd were also potentially under threat.

Leggetts Drive has been both directions, and the rural fire service has advised residents of nearby Sheppeards Drive evacuate if it is safe to do so.

Jo Wright, who lives on Leggett Drive, said her family were extremely concerned.

“My husband has just spoken to the fireys, and they are in our backyard pumping water from our dam.

“Our sheep have been let out too, so I hope they are OK,” she added.

“My husband and son can’t even get home. Hopefully they can control it without too much damage and looking after themselves too. They do a fabulous job,” she said.

Wayne Edwards, who lives in Richmond Vale, early this afternoon said the fire was a mere 100m from his house.

“It’s heading east, but if the wind swings south we may be in trouble.”

Meanwhile, residents of the area were jumping onto social media, offering to care for the affected farms’ livestock.

“If anyone’s horses are in danger due to the fires, we have a paddock here at Cardiff that a horse could come to,” Brydie Minor wrote on Facebook.

The cause of the fire, which has been burning since yesterday morning, has yet to be determined.

A second NSW fire, burning near Nabiac on the mid-north coast, has also been declared a watch and act blaze this afternoon.

A Rural Fire Service spokesman said was the fire, which has burnt 1662 hectares so far, was in the process of being controlled and no property had yet been destroyed.

Meanwhile Sydney was under a total fire ban today, with temperatures hitting 33C at midday.

Former prime minister Tony Abbott took emergency leave from parliament to join dozens of firefighters in his electorate battling to re-contain a blaze at Beacon Hill, in Sydney’s northern suburbs, as wind gusts threatened to fan dangerous fire spots.

The Manly Daily was told Mr Abbott helped avert a crisis when embers set fire to a property’s fence, with homeowner Barry Cafe singing his praises for saving his house.

“I told everybody, ‘I’m fine, Tony’s here,” he said, adding that it is not every day a former prime minister saves your home. “He’s a top bloke … We couldn’t do without them (RFS).

Mr Abbott, who was working with the Davidson Rural Fire Brigade by driving a truck and fighting spot fires in Beacon Hill, played down the situation, telling reporters: “Obviously it was an interesting situation, but it appears now to be under control.”

He later told The Daily Telegraph’s Sharri Markson: “It’s always good to serve the community as a member of the RFS. For me, it’s always an honour to be with the members of the Davidson brigade.”

By 4pm yesterday, firefighters were putting the final touches on a backburn to protect residents around the Beacon Hill fire from any property damage.

In Sydney’s west, Live Traffic NSW reported at 2.35pm that Castlereagh Rd in Agnes Banks has been closed due to a bushfire, between The Driftway and Drift Rd.

Motorists are advised to use Londonderry Rd as an alternative, and Route 678 buses are diverting around the area and missing one stop in each direction.

Some areas of the state were tipped to reach the mid-30s today and gusty west-north-westerly

winds are expected to elevate the fire danger.

Crews from the RFS and Fire & Rescue NSW poised from early in the day to respond to any new outbreaks which occur, including calling in aircraft assistance.

Fire bans were put in place in the greater Sydney, north coast, greater Hunter and northwestern districts.

Sydney is forecast to come close to its warmest day on record this early in September, with the Bureau of Meteorology expecting the mercury to climb to 32C — 12C above average for the month.

The total fire ban, the first for the 2017-18 season, will probably last one day in the Sydney region but areas further north may be under restrictions for longer, a RFS spokesman said.

The conditions which helped the Beacon Hill grassfire spread are only a prelude to what could be a far more dangerous Wednesday, an RFS spokesman told AAP today.

“(Those regions) have been issued with severe fire danger rating with forecast conditions of temperatures in the mid-30s and winds gusting up to 75km/h from the northwest,” he said.

“It could be a bad day — given the conditions we’ve had so far haven’t been close to that.”

A cool change is predicted to blow through from the southwest in the late afternoon but, with no rain forecast, it’s just another day closer to what’s expected to be a particularly dangerous fire season.

The state’s forests, including the Central and Great Dividing ranges and the entire eastern seaboard, are full of dry fuel, the RFS spokesman said.

“It won’t take much for a fire to start. “Given conditions … they’ll be able to spread quickly, hot and fast.”

EARLIER TODAY

A number of areas in the state have already declared the danger period, but the rest of the state will be on alert after October 1, the official first day of bushfire season.

However this afternoon some immediate relief was on offer, with BOM forecaster Elli Blandford saying temperatures will drop tomorrow and snow is expected on the alps.

“Once this cold front pushes through, we’ll see temps drop dramatically, with tomorrow’s max to be 18C, it is going to be relatively cold,” she said.

“We will see some showers moving through with this cold front, we will have snow over the alps. We have quite a good chance of getting some snow, we’re forecasting snow at levels down to 600m.”