As night fell along the Princes Highway on the NSW south coast, thousands of people laid out bedding, pulled up camping chairs, walked their dogs and put their children to sleep on the side of the road as a long convoy of bushfire evacuees waited for the road to re-open.

By Thursday evening most had been waiting for hours in bumper-to-bumper traffic stretching for kilometres from the small coastal community of Milton to at least Ulladulla.

Hundreds of frustrated people at a road block south of Nowra. Many waiting 10+ hours to travel sth on the Princes Highway to evacuate loved ones. These people are going back to their cars to sleep. Many are already there, waiting, angry #NSWfires #AustraliaBurning pic.twitter.com/YMOA15ZJJO — Hilary Whiteman (@hilary_whiteman) January 2, 2020

Near the evacuation centre in Ulladulla, Heidi McClelland watched over her two-year-old son Spike, asleep in blankets, while her mother and 10-week-old son Johnny remained in the car.

Ms McClelland, 35, left her home in Dalmeny, south east of Eurobodalla, at 11am on Thursday after being told at a town meeting on Wednesday that young families should depart ahead of worsening weekend conditions.

READ MORE NSW fires: State of emergency declared as PM urges calm amid mass exodus

Her partner Patrick has stayed behind to defend their property as the foursome try to reach Woollongong.

"(We were told) it's just going to be catastrophic on Saturday - so pretty much just get in the car and go," Ms McClelland said.

While some locals have offered them a place to stay for the night, "we're just staying in the line so we don't lose our spot," she added.

MILTON: thousands of cars banked up from Milton to Ulladulla tonight. Drivers and passengers asleep in cars - waiting to be escorted along the Princes Highway by police. But fallen trees and spot fires continue to cause delays #WINNews6pm @WINNews_Woll @WINNews_ACT pic.twitter.com/NmFlovWMEm — Samara Gardner (@SamaraMGardner) January 2, 2020

Melva Kerr, 65, was travelling with her daughter Elle Kerr, 31, from Batemans Bay to Sydney when they got stuck at Ulladulla.

"If they don't open it tonight I think we're all just sleeping in our cars but as soon as it opens hopefully we can get through," Ms Kerr said.

She felt many people were determined to stick out the long wait until the roads open because of the dangerous forecast conditions.

Emergency Services have started escorting vehicles on the Princes Hwy, northbound, btwn Milton & Nowra. Due to heavy traffic, this process will take at least 6 – 7 hours to complete. The hwy may close at short notice due to firefighting operations. #nswrfshttps://t.co/UxB9vJaAnC pic.twitter.com/SbXjyvxTch — NSW RFS (@NSWRFS) January 2, 2020

NSW will come under under a statewide total fire ban on Friday and Saturday amid the third state of emergency of the bushfire season.

Holiday-makers in the alps and between Nowra and the Victorian border were asked to be out by Friday night.

Police began escorting convoys of 100 vehicles from communities east of the Princes Highway north towards Nowra, with the first leaving about 9pm on Thursday, a Rural Fire Service spokeswoman said.

The RFS and tree fellers were on Thursday working to make the Princes Highway safe following two incidents of falling trees, the spokeswoman said.

Morgan Alexander and Sam Hinwood, both in their 20s, were part of a group of six people, and dog Solo, who had been waiting in Milton for the road to open up since 2pm on Thursday.

They had been holidaying in Kioloa when they heard several routes to leave had closed. They were running low on petrol, the power went out and they had to pool their cash to pay for supplies.

Impossible to properly convey the devastation and loss around the #SouthCoast due to #bushfires This was beside the #princeshighway earlier today before it was again closed #NSW #australia #staysafe pic.twitter.com/3hMWtrAIYP — Douglas Isles (@douglasIsles) January 2, 2020

Lines at the local IGA store stretched out the front door when the power went out, which Ms Alexander described as "a bit apocalyptic".

"I just feel lucky that we've been safe," Mr Hinwood said.

Ulladulla locals Glen Dorrell, 43, his son Owen Dorrell, 13 and Dylan Barkle, 22, walked up and down the long line of cars to invite stranded motorists to a free barbecue in Mr Dorrell's yard.

Mr Dorrell, known as Dozza, told AAP the act of generosity was prompted by the "Aussie spirit".

"People are sitting here, they can't eat lunch, they can't use their cards, so Dozza just decided to throw on a free barbecue for everyone. They all deserve it," Mr Barker said.