The authorities expect conditions to worsen on Friday and Saturday.
Motorists joined long queues as huge numbers of people evacuated from New South Wales and Victoria amid the threat of Australia's ongoing bushfire crisis.
There were reports in the town of Batemans Bay some customers waited up to five hours at supermarkets, which had been operating with a limited supply of stock, as well as petrol stations, which saw an increased demand for fuel as motorists left the area.
New South Wales Premier Gladys Berejiklian said a third state of emergency will be declared from 9am on Friday morning before extreme conditions return to the state by Saturday.
Tourists in a 250km (155 miles) stretch from the New South Wales South Coast to Victoria's East Gippsland have also been advised to leave the region within a 24-hour period before unfavourable weather conditions return.
At a news conference in Sydney, Australian Natural Disaster and Emergency Management Minister David Littleproud urged those in the area "to be prepared and to act now".
At least 18 people have died, 1,200 homes have been destroyed and about five million hectares (12.35 million acres) of land have burned nationwide from the wildfires since September.
Meanwhile, Australian Prime Minister Scott Morrison on Thursday defended his government's record on tackling climate change as he faced questions about the wildfires which continued to threaten large parts of the country.
Morrison spoke during a press conference as reporters continually asked if the government was doing enough in the face of climate change and a devastating bushfire season.
"No response by any one government anywhere in the world can be linked to any one fire event," he said.
Morrison said Australia had successfully beaten its goals for reducing its carbon emissions for 2020 as laid out by the Kyoto 2020 agreement.
He acknowledged this fire season had been "extraordinary" and hoped it would not repeat next year, reiterating the focus now was to get people evacuated.