More than 100 fires were still active Sunday in New South Wales and Queensland (Northeast) states, and some were still under control.
A drop in nighttime temperatures, however, provided a day of respite for firefighters and the public.
In the coming days, due to poor weather conditions, these fires are expected to spread within these two states, including around Sydney, and affect the State of Western Australia (West).
Since Friday, three people have died and 150 homes have been destroyed while five missing persons have been found.
However, because of the unpredictable nature of these fires, the authorities do not exclude the possibility of new people being reported missing, said Greg Allan, spokesman for firefighters in rural areas of New South Wales.
High temperatures, low humidity and strong winds are expected in the middle of the week, which should help fuel fires that can not be controlled by then, the authorities said.
"In these conditions, these fires will spread quickly and threaten lives and homes," warned New South Wales firefighters in a statement.
"The weather will be bad, if not worse than the one we had on Friday and it could affect a much larger area, including densely populated areas like Sydney," they said.
Shane Fitzsimmons, fire chief for New South Wales, said dozens of additional firefighter teams will be deployed Monday to prevent a worsening of the situation.
Sunday, in Queensland, more than 1,200 fire soldiers fought against about fifty fires with air support of 39 aircraft.
– "unprecedented" situation –
"Queensland generally does not have a fire season like this year or we experienced last year," state premier Annastacia Palaszczuk told reporters.
The Australian government has provided aid of A $ 685 (€ 622) to the thousand people who have been forced to leave their homes.
The excitement was high on Sunday at an evacuation center in the city of Taree, located in one of the most affected areas of New South Wales. A man broke down in tears kissing Prime Minister Scott Morrison.
"People are under enormous pressure," Morrison, whose government has downplayed the threat of climate change, told reporters.
He was arrested at a fire command center in Wauchope, New South Wales.
According to an Australian newspaper, a man said: "Climate change is real, do not you see?"
Such fires occur every year on the huge island-continent during the spring and summer in Australia.
But this year, they have been extremely numerous, violent and early. The first occurred in September, from northern New South Wales to the tropical areas of Queensland.
If this start of the season is dramatic, scientists are worried for the next few months. According to them, climate change and weather cycles generate high temperatures, strong winds and drought.
The deadliest fires in Australia date back to 2009. That year, 173 people died in bush fires in Victoria.
Ross Bradstock, Environmental Bushfire Management Center at Wollongong University, described the situation as "unprecedented" because currently affected areas have rarely, if ever, experienced such a situation. fires.
"Unfortunately, given the weather forecast for the coming week, the crisis could worsen and spread south into areas that are ready to burn due to intense drought," he said.