'It's too late to leave': Emergency situation in Sydney's north as NSW fire crisis escalates

Residents in several NSW regions are being told it’s too late to leave as more than 78 bushfires rage on Tuesday.

Thirteen emergency warnings have been issued for those fires, including two in Sydney’s north-west.

The Rural Fire Service says a fire has broken out at Canoon Road at South Turramurra. The fire is spreading quickly and properties are under threat.

"It is too late to leave," the RFS said in its warning message on Tuesday afternoon.

"Seek shelter as the fire approaches. Protect yourself from the heat of the fire.”

Transport for NSW is advising those in inner-city Sydney and the Illawarra to leave work early ahead of the southerly change which is due to hit between 5 and 6pm.  

"High winds are predicted to sweep into Sydney and the Illawarra this afternoon which on top of the significant heat may start to affect the public transport network," Transport NSW said.

The authority added that trains will be operating under speed restrictions due to the heat and winds may affect roads and the rail network.

Flights have also been cancelled due to the smoke and dangerous weather conditions with Nine News reporting planes travelling from Sydney to Port Macquarie and Coffs Harbour have been grounded.

People have been urged to check with their airlines to see if flights have been affected.

Authorities say conditions are only going to get worse across NSW, with five emergency warnings issued for bushfires from the mid-north coast to the Queensland border on a day where millions face "catastrophic" fire danger.

More than 50 fires are raging across NSW with 30 not contained.

The NSW Rural Fire Service on Tuesday elevated five fires to "emergency" warning level - two near Taree on the mid-north coast, one near Port Macquarie and another two at Torrington in the state's far north.

A blaze at Thunderbolts Way in Bretti, northwest of Taree, is burning across 10,000 hectares and is out of control, while residents at Nowendoc and Mount George have been told "it is too late to leave".

Another out-of-control fire at nearby Hillville is burning across nearly 20,000 hectares.

There are also emergency fires further north, at Llangothlin north of Armidale, and Torrington north of Glen Innes, with the latter blaze already razing 60,000 hectares.

A fifth emergency was also issued at Carrai East in Willi Willi National Park, northwest of Port Macquarie, for an out-of-control fire over 75,000 hectares.

The fire is heading towards east towards Kempsey, with those in the town's west under threat.

One million hectares of bushland burning

"We are certainly starting to see an increase in fire activity and therefore the fire danger is increasing accordingly," Rural Fire Service commissioner Shane Fitzsimmons told reporters in Sydney.

A Gloucester fire crew member fights flames at Koorainghat on Tuesday. Source: AAP

"The reality is conditions will simply continue to get worse and deteriorate over the coming hours and particularly into this afternoon when the combination of the hotter temperatures, the drier atmosphere and the strengthening winds all come together to drive fire."

Mr Fitzsimmons said the day was unfolding as predicted with a million hectares burning.

"We were expecting the hot dry winds to exacerbate fire spread and behaviour - and that's exactly what we're seeing unfold at the moment."

NSW is dealing with unprecedented fires during what the emergency services minister says could be the most dangerous bushfire week in Australia's history.

Firefighters face ‘really long’ night

Firefighters have a long night ahead of them with strong winds expected to reach northern NSW fire grounds around midnight.

The Bureau of Meteorology on Tuesday afternoon warned things will get worse before getting better.

BOM state manager Ann Farrell says a low-pressure system moving across the state is bringing "strengthening, hot, dry winds" that will increase fire danger on Tuesday evening.

Ms Farrell says a dangerous wind change is expected to hit Wollongong about 5pm, southern parts of Sydney about 6pm and Port Macquarie by midnight.

The change will bring vigorous southerly winds which could rapidly expand the length of fire fronts.

"Winds that are currently moving from the northwest are going to change to southerly and track up the coast," she said in Sydney.

"And when that change happens ... the fires will be fanned in a different direction. They'll be very gusty and quite unpredictable at times. So that will make fire conditions much more dangerous."

Ms Farrell said the wind change could see temperatures drop about 10 degrees. 

"Things are going to be pretty difficult for some time tonight before we see any real improvement in fire fighting conditions," she said.

Thousands of firies pushed to the limit

More than 3000 firefighters and 80 aircraft will potentially be involved in battling the blazes.

Premier Gladys Berejiklian has urged residents to heed warnings and head for safety.

"We need to make sure every community member takes the opportunity to assess the situation and act with precaution in every possible manner," she told reporters in Sydney.

A catastrophic fire danger rating - the highest possible level - is in place for the Greater Sydney, Greater Hunter and Illawarra-Shoalhaven regions.

So far on Tuesday, there have not been any new fires in the "catastrophic" regions.

NASA satellite images show hot, dry and windy weather conditions as bushfires burn in the eastern part of NSW. Source: NASA via AAP

Temperatures in the high 30s, low humidity and strong winds - coupled with the drought - means the state faces "horrendous conditions", according to the RFS.

Mr Fitzsimmons is urging people to relocate if in the path of a fire. He said winds across the ranges were averaging up to 50km/h with gusts exceeding 70km/h.

RELATED: 'Absolute tragedy': Koala numbers decimated after bushfires destroy key habitats

A fire near Nimbin west of Mullumbimby is developing, the commissioner said, while making special mention of a blaze in the Wollemi National Park north of Sydney.

"If you are in the area of Mellong, St Albans and Upper MacDonald, and your plan is to leave, leave now to a safer location," the RFS said in a "watch and act" alert.

A week-long state of emergency has been declared in NSW and the Australian Defence Force is on standby to provide support - including for search and rescue operations.

Some 600 schools have been closed.

"Leaving early and well ahead of any fire in your area is the safest option," Mr Fitzsimmons stressed.

"Safest options might include going to the local shopping centre, going into town, where you're not in the bushfire-prone area."

With embers known to jump 20 to 30 kilometres in front of a catastrophic blaze, firefighters attempted tactical back burning operations on Monday night, but Mr Fitzsimmons said their impact would be "tenuous at best".

There are also extreme fire danger ratings - the second-highest level - for the north coast, southern ranges, central ranges, New England, northern slopes and northwestern areas.

The bushfires, which hit hard on Friday, have claimed three lives and destroyed at least 150 homes in the state's north.

Prime Minister Scott Morrison said he hoped Tuesday would be a "boring day" but said authorities were well-prepared and on high alert.

–– with AAP

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