Australians feel the heat as bushfire threat flares up

Severe to extreme heatwaves will grip swathes of Australia, bringing conditions not seen since the Black Summer bushfires.

For some areas across South Australia, Victoria, the ACT and NSW, temperatures will reach levels not felt in the past couple of years, the Bureau of Meteorology warns.

Starting on Wednesday, South Australia, Victoria and inland parts of NSW will cop the brunt of the heat, with Adelaide and Melbourne facing temperatures reaching 42C while inland Australia could reach 45C, senior meteorologist Angus Hines said.

The heat is expected to linger in SA and climb in Canberra to a forecast 37C on Thursday before rising again for the capital and in Melbourne and parts of central Australia on Friday.

Sydney will swelter through a 39C maximum on the expected final day of the heatwave on Saturday, with some western suburbs reaching 44C.

The conditions are set to be worst since the catastrophic 2019-20 summer bushfires that killed more than 30 people and burned through millions of hectares.

"Heat is just one ingredient that leads to elevated and dangerous fire danger, and we do expect to see some pretty significant fire weather during the course of this heatwave," Mr Hines said.

Dry conditions across the nation mixed with fairly breezy winds and the potential for lightning strikes could be enough to whip up blazes.

"If any bushfires do get going under these conditions, they can spread extremely quickly and be very difficult or impossible to control and contain," Mr Hines said.

As the mercury rises, fire dangers are expected to reach extreme levels in South Australia, Victoria, and inland NSW with total bans expected to be in place across much of the country.

The SA government has issued a Tier 1 Code Red starting Tuesday to Thursday to provide welfare checks and rapid support to vulnerable and isolated residents, including the homeless.

Victoria's State Control Centre has issued an advice warning for the entire state on Wednesday, with Emergency Management Commissioner Tim Wiebusch warning of a challenging three or four days.

"We are likely to see severe to extreme intensity heatwaves at a level that we have not seen since 2019/20, and we need Victorians to heed the advice warning," he told reporters on Tuesday.

While the fire conditions are not at the same level as six years ago, authorities are seeing a number of fires starting in recent days off the back of underlying dry conditions.

"There is a very real risk that we could see serious fires over these coming days," he said.

Mr Wiebusch urged people to stay safe at waterways and take precautions such as drinking plenty of water and sheltering during the hottest parts of the day.

Those most at risk included people aged over 65, babies and young children, pregnant women, people with acute or chronic health conditions and those who were socially isolated, Victorian Deputy Chief Health Officer Evelyn Wong said.

"The health impact of heat is cumulative, and this means that with consecutive hot days and warm nights, it will be make it harder for the body to cool down," Dr Wong said.

Soaring temperatures are expected ensure record spikes on the electricity grid as Australians crank up the air-conditioning, increasing the risk of unplanned outages, energy supplier AusGrid said.

The heatwave comes after 2025 was named Australia's fourth-warmest year on record, with the temperatures 1.3C above the 1961-90 average, and 2024 the nation's second-warmest year.

Australia's warmest year was 2019, when the national annual average temperature was 1.51C above average.