Three people are now confirmed dead as the NSW / QLD bushfires continue to burn, with two classified as "emergency warning" level.
"If a fire starts and takes hold during catastrophic fire danger conditions, lives and homes will be at risk", the warning continued.
Sydney is facing a "catastrophic" fire threat, authorities said on Sunday, as firefighters in eastern Australia raced to prepare for worsening conditions after ferocious bushfires devastated communities.
Firefighters found another body on Saturday morning in a burned vehicle near Glen Innes, a victim of the same fire, officials said.
Mr Fitzsimmons said along with the 1300 firefighters on the ground right now from across Australia and New Zealand, they were in contact with colleagues from Canada and the United States for possible help in light of Tuesday's predicted forecast.
"There are other states where the risk is also high", Morrison said, adding that a nationwide emergency meeting of fire and emergency services chiefs had been called earlier that day.
In the New South Wales town of Taree, more than 300 people evacuated overnight to a social club, including Club Taree's chief executive Morgan Stewart.
"What really hit me today is even though some people know that their homes are OK they are still extremely traumatised by what they have experienced", she said.
One of the fires in Crowdy Bay National Park, north of Taree has already burned through nearly 12,000 hectares, while the other at Mount Nardi National Park is 2200 hectares in size and out-of-control.
They were also in discussions with the Australian Defence Force.
Vivian Chaplain, 69, died after a bushfire swept through Wytaliba.
Authorities warned severe fire danger was expected on Wednesday, with little reprieve this year.
Several fires were also reported raging in the state of Queensland, north of NSW, with at least one of them classified at the emergency level.
"It is a sobering reminder of what is ahead, with the outlook indicating the next three or four months is dominated by above-average temperatures, below-average rainfall and unfortunately there is no meaningful signal anywhere for drought-breaking, relieving rain", he said.
In some areas, residents were stuck and told to simply "seek shelter as it is too late to leave".
Thousands of residents in the state's north were forced to flee for their lives, and multiple buildings, including a school at Bobin, in the northwest, are believed to have been destroyed.
The carers estimate at least 10 days will be needed to assess the full damage to the koala population.
Acting Fire Commissioner Mike Wassing said their focus on Sunday was on Cobraball near Yeppoon. "We now have 31 out of 37 districts in Western Australia in the high fire rating, and three of those will go to catastrophic in the days ahead".
A statewide total fire ban has been issued for Monday and Tuesday. More than 150 properties have already been lost to the fires.
Some firefighters have suffered heat exhaustion, one broke a leg and another had an ankle injury.
The current disaster has not wreaked the human devastation of Australia's worst recent bushfires, the Black Saturday fires that killed 173 people in Victoria state in 2009, with some experts attributing that to better early warning systems.