The rising temperatures in South Australia prompted “catastrophic” alerts –the highest danger rating on Wednesday. The temperatures neared 45C and wind speed upwards of 90 km/h.
Parts of Victoria have been issued the same warning for Thursday, while the threat in Tasmania is also increasing.
Six people have died since last month in massive bushfires which are burning elsewhere in the country.
The fires in New South Wales (NSW) and Queensland have destroyed over 500 houses.
Officials switched off electricity to about 10,000 homes and businesses to reduce the risk of new fires. Such blazes are most commonly sparked by winds bringing down power lines.
Australia’s largest city, Sydney, was also blanketed by bushfire smoke on Tuesday, causing dozens of calls to paramedics for respiratory related health problems.
With no significant rainfall predicted for the next few months, officials have warned of tough months ahead.
The longer dry period has brought scientists and experts to the conclusion of climate change.
Climate change had led to an increase in extreme heat events and raised the severity of other natural disasters, such as drought.
Last year the nation experienced its warmest summer on record. Official figures also show 2018 and 2017 were Australia’s third and fourth-hottest years on record respectively.