More than half of Australia is set to swelter in blistering temperatures in what is expected to be the worst heatwave since the devastating black summer bushfires.
The Bureau of Meteorology warned that dry, hot conditions would create extreme fire conditions across several states as temperatures topped 45C in parts of the country.
The senior meteorologist Angus Hines said that western and south-western NSW were likely to experience multiple consecutive days of hot conditions this week, with temperatures in Sydney to climb into the high 30s or low 40s on Saturday.
“We’ll be seeing 39C or 40C right through the Sydney area for Saturday,” he said.
In South Australia, temperatures were forecast to reach as high as 47C by Thursday in the coastal city of Port Augusta and Tarcoola in the far north.
The BoM said Adelaide would experience a maximum temperature of 42C on Wednesday, with the heat remaining in the low-40s across the metropolitan region into Thursday.
The heat band had been building across Western Australia for days and would extend into South Australia, New South Wales and Victoria from Tuesday.
As the mercury rises, fire danger was 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 conditions were set to be the worst since the catastrophic 2019-20 summer bushfires that killed more than 30 people and burned through millions of hectares.
“For the three-day period from Wednesday through to Friday this week, our heatwave warnings are extensive” Hines said.
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“All the way from northern South Australia down to the south-east … through the ACT, southern NSW and eastern parts of Victoria, so it’s a prolonged run of very hot days as well as hot nights across this entire area through the second half of this week,” he said.
“If any bushfires do get going under these conditions, they can spread extremely quickly and be very difficult or impossible to control and contain.”
Hines said Victoria and South Australia would experience the “brunt of the heat on Wednesday.
On Tuesday afternoon, Michael Efron, a senior meteorologist at the Bureau of Meteorology, said temperatures would be in the low to mid-40s across much of Victoria on Wednesday.
Efron predicted a top temperature of 42C in Melbourne, which would be the city’s first 40C day in January since 2020.
Temperatures would ease in Melbourne on Thursday, but remain high in the north and east of the state, with potentially record-breaking temperatures as high as 46C.
“In addition to that, we are going to see some thunderstorm activity,” said Efron, which he said would bring little rain and could lead to bushfires.
Hot conditions and “gusty, erratic” winds were expected to redevelop over much of Victoria on Friday, elevating the fire risk.
An advice warning to prepare for extreme heat was in place for the whole of Victoria, said the state’s emergency management commissioner, Tim Wiebusch.
“People need to prepare and charge their devices now and make sure you continue to do that over these coming days.”
Soaring temperatures were expected to ensure record spikes on the electricity grid as Australians crank up the air conditioning.
“There is an increased risk of unplanned outages during prolonged heatwave conditions, due to an increase in demand on the grid,” said Matthew Sweeting, from energy supplier Ausgrid.
The bureau defines a heatwave as three consecutive days of above-average temperatures.
The heatwave comes after another record year, with 2025 being Australia’s fourth-warmest on record, with temperatures 1.3C above the 1961–1990 average.
“This follows Australia’s second-warmest year in 2024,” said the climatology specialist Nadine D’Argent.
“South Australia and Western Australia both recorded their third-warmest years.
“Between January and March, and between October and December, large parts of Australia experienced heatwave conditions, reaching extreme severity at times.”
Australia’s warmest year was 2019, when the national annual average temperature was 1.51C above average. The climate crisis has increased the frequency and severity of extreme weather events, including heatwaves.
