Emergency bushfire warnings have been issued for blazes in NSW's Shoalhaven and Upper Hunter regions as the Rural Fire Service prepares for worse to come as summer officially begins.

The so-called Currowan fire burning north of Batemans Bay has already ripped through 7000 hectares and is being fanned by strong westerly winds on Sunday afternoon.

The Currowan Fire is burning north of Batemans Bay. It's now burnt around 7000 hectares of bushland and is spreading quickly towards the east, generating lots of smoke along the coast. Updates at https://t.co/S1fx90uJbi #nswrfs #nswfires pic.twitter.com/dwrJ9IY7ki — NSW RFS (@NSWRFS) December 1, 2019

"The fire has crossed the Clyde River," the RFS said in an emergency warning after 3pm.

"If you are in the area to the west of the Princes Highway between Turmeil and East Lynne seek shelter as the fire impacts. It is too late to leave."

EMERGENCY WARNING - Currowan fire (Shoalhaven LGA)

Fire activity increased & has crossed Clyde River. If you're in the area west of Princes Hwy between Turmeil & East Lynne, seek shelter as fire impacts. It's too late to leave. #nswrfs #nswfires #alert https://t.co/es8I6vvg3i pic.twitter.com/TqOzGLS3TF — NSW RFS (@NSWRFS) December 1, 2019

Another emergency warning has been issued for a blaze southwest of Merriwa in the Goulburn Rivers National Park.

"There are numerous rural properties in the area which may come under threat," the RFS said on Sunday afternoon of the Meads Creek West fire.

"If you are in the area southwest of Merriwa and you are not prepared, leave now towards Merriwa."

EMERGENCY WARNING - Meads Creek West fire (Upper Hunter LGA)

Fire burning to south west of Merriwa in the area of Goulburn National Park. If you're in the area south west of Merriwa & you're not prepared, leave now towards Merriwa. #nswrfs #nswfires #alert https://t.co/yCrUBM8sco pic.twitter.com/8Ltegxj5Tl — NSW RFS (@NSWRFS) December 1, 2019

Two million hectares of land have been burnt since July in more than 7000 fires which have raged across the state in the "most challenging bushfire season ever".

Six lives have been lost while 673 homes and 1400 other buildings have been destroyed.

A total fire ban has been issued for Monday across the far north coast, Greater Hunter and New England regions due to forecast hot and windy conditions.

"While it's expected to be cooler tomorrow, it's going to be very windy in many areas," the RFS tweeted.

"This will present challenging conditions for several days with so many fires."

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There'll be "very high" fire danger on Monday from the Illawarra and Shoalhaven up through Sydney and along the coast to the Queensland border.

The New England, northern slopes and northwestern fire areas will also face "very high" danger.

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There were three watch and act alerts in place on Sunday afternoon along with the two emergency warnings.

The North Black Range blaze west of Braidwood is over 20,000 hectares but is being controlled.

"The fire is burning towards the areas of Jembaicumbene, Bendoura and Majors Creek," the RFS said at 3.30pm.

Firefighters and aircraft are working to slow the spread of the fire burning south of Katoomba. It's creating a lot of smoke - but there is no immediate threat to homes in the Blue Mountains. #nswrfs #nswfires pic.twitter.com/SACddMe5Vt — NSW RFS (@NSWRFS) December 1, 2019

The other watch and act alerts were near Yerranderie in the southern part of the Blue Mountains.

Firefighters and aircraft were also working on Sunday afternoon to slow a fire burning south of Katoomba.

While it was creating a lot of smoke there was no immediate threat to homes in the Blue Mountains, the RFS advised.

There were some 150 grass and bush fires burning across NSW on Sunday with a third of them uncontained.