Worst Since Black Summer: Heatwave Pushes Southern Australia to the Limit

A fierce heatwave described by forecasters as the worst since the Black Summer bushfires is gripping southern Australia, driving temperatures into the mid-40s Celsius, elevating fire danger and placing heavy strain on health services and electricity networks.

The Bureau of Meteorology says the multi-day event will peak between Wednesday and Friday, with severe to extreme heatwave conditions stretching from South Australia across Victoria and into southern New South Wales, the Australian Capital Territory and parts of Tasmania. The hot air mass, which first built over inland Western Australia, is forecast to push some inland and northern areas of South Australia and Victoria to 46 or 47 degrees Celsius.

“This is a significant, prolonged heatwave event,” senior meteorologist Dean Narramore said in a video briefing. “We’re looking at maximum temperatures running around 8 to 16 degrees above average for large parts of South Australia and Victoria, with several days in the mid-40s and very warm nights offering little relief.”

Dangerous heat, day and night

In Adelaide, temperatures are forecast to reach the low 40s on Wednesday, with several days in the high 30s to follow. Inland South Australian towns including Port Augusta, Renmark, Port Pirie and Murray Bridge are expected to climb to 44 to 46 degrees at the peak of the heat.

Melbourne is forecast to reach around 41 degrees on Wednesday before a brief cool change, while northern and western Victorian centres such as Mildura, Swan Hill, Horsham, Bendigo and Shepparton are set for 44 to 45 degrees across multiple days.

Overnight temperatures in many affected areas are predicted to remain in the high teens to mid-20s, a pattern that the bureau says is a defining feature of a heatwave and a key factor in health risk.

“A heatwave is not just about extreme daytime temperatures,” the bureau’s heatwave guidance notes. “It is a period of at least three days where both maximum and minimum temperatures are unusually high, leading to accumulated heat stress on the body and the environment.”

The bureau has issued severe and, in some inland locations, extreme heatwave warnings. Under Australia’s national framework, a severe heatwave is considered dangerous for vulnerable people, while an extreme heatwave is hazardous even for healthy, well-prepared individuals.

Echoes of Black Summer

Officials and major media outlets have repeatedly invoked the Black Summer bushfire season of 2019-20 in describing the current event. The bureau has warned Victoria, South Australia and southern New South Wales face their most significant heatwave conditions since those that preceded and accompanied the Black Summer fires.

That season burned an estimated 24 million to 26 million hectares across the country, destroyed more than 3,000 homes and caused at least 33 direct deaths, with subsequent health studies attributing hundreds more fatalities to smoke pollution. Record-breaking heatwaves in 2019 helped dry out vegetation and prime the landscape for the catastrophic fires that followed.

Forecasters stress that the current heatwave does not mean a repeat of Black Summer is inevitable. Instead, the comparison reflects the intensity and duration of the heat, the temperature anomalies relative to average and the breadth of the area affected.

“The reference point is the scale of the heat stress, not a prediction that fires will reach the same extent,” one bureau climatologist said. “But elevated fire danger is certainly a concern, especially as winds increase later in the week.”

Health officials warn of life-threatening conditions

Health authorities across multiple states have urged residents to take the heat seriously, emphasising that heatwaves are Australia’s deadliest natural hazard in an average year.

“Extreme heat can be life-threatening,” New South Wales Health’s director of environmental health, Dr Stephen Conaty, said in a recent advisory on hot weather. “It’s particularly dangerous for people over 65, babies and young children, pregnant women, people with chronic illnesses, and those who are socially isolated or working outdoors.”

Victoria’s Department of Health warns that extreme heat and heatwaves can trigger potentially fatal conditions, including heatstroke and heat exhaustion, and can worsen existing heart and respiratory diseases. The agency notes that intense heat events can also disrupt power supply, public transport and other critical infrastructure.

Standard advice from state health agencies includes staying indoors during the hottest parts of the day, using air conditioning or fans where possible, drinking plenty of water, closing blinds and curtains early to keep homes cool, avoiding strenuous physical activity and checking regularly on elderly neighbours, relatives and people who live alone.

But public health experts acknowledge that these recommendations are harder to follow for people in substandard housing or those worried about high power bills.

“Many low-income households and renters are living in dwellings that are not designed for this kind of sustained heat,” one heat-health researcher said. “They have poor insulation, little shading and sometimes no air conditioning at all. The risk is not evenly shared.”

Urban hot spots and energy stress

The heatwave is expected to be felt most intensely in inland and regional areas, but major cities face particular challenges due to the urban heat island effect. Built-up suburbs with extensive concrete and limited tree cover can remain several degrees hotter than surrounding rural areas, especially overnight.

In cities such as Melbourne and Adelaide, outer western and northern suburbs with fewer green spaces commonly record higher temperatures than coastal or inner-city neighbourhoods. That pattern, researchers say, amplifies existing social and economic inequalities, as lower-income communities are more likely to live in hotter areas and older housing.

Energy operators are preparing for a surge in electricity demand as households and businesses turn on air conditioning through the day and, unusually for many areas, into the night. Multi-day heatwaves are particularly taxing on the grid because demand remains high after sunset and infrastructure such as transformers and power lines has less opportunity to cool.

Authorities have not announced any load-shedding, but they are urging consumers to use energy efficiently during peak times and to have contingency plans in case of localised outages, especially for people dependent on medical equipment.

Fire danger elevated across several states

Fire agencies in South Australia, Victoria, New South Wales and Tasmania have warned of high to extreme fire danger in multiple districts as the heat combines with dry fuels and, later in the week, strengthening winds.

Victoria’s Country Fire Authority has declared total fire bans in some northern and western fire districts and is encouraging residents in bushfire-prone areas to revisit and, if necessary, activate their bushfire survival plans.

“Now is the time to know what you will do if a fire starts near you,” a CFA spokesperson said. “Conditions can change quickly in these temperatures, and leaving early is always the safest option.”

Similar messages have been issued by the South Australian Country Fire Service and New South Wales Rural Fire Service. In Tasmania, authorities have highlighted elevated fire danger along parts of the east coast, Midlands and central north, with the risk expected to persist even as a cooler change arrives with gusty winds.

A hotter baseline

The current heatwave is unfolding against the backdrop of a steadily warming climate. Bureau of Meteorology data show that Australia’s average land temperature has risen by about 1.5 degrees Celsius since 1910. The country’s climate summary for 2025 found it was the fourth-warmest year on record, about 1.23 degrees above the 1961-1990 average, while 2019 remains the hottest year.

In recent years, the bureau’s State of the Climate reports and public communications have underlined that heatwaves in Australia are becoming more frequent, lasting longer and reaching higher peak temperatures. The number of extremely hot days has increased across most of the continent.

Climate scientists say that means events once viewed as rare are occurring more often and affecting more people.

“What we’re seeing now is a heatwave on top of a higher baseline,” a bureau climatologist said. “That raises the floor as well as the ceiling. Nights don’t cool as much, seasons start earlier and end later, and the cumulative stress on people, ecosystems and infrastructure is greater.”

A test of adaptation

Since the Black Summer bushfires, state and federal governments have introduced or expanded a range of measures aimed at better managing extreme heat and fire risk. These include the National Heatwave Warning Framework, more detailed bureau heatwave forecasts, upgraded emergency apps, and local heat-health plans designed to identify and support at-risk residents.

This week’s heatwave will test how well those systems function when much of southern Australia is exposed to extreme conditions at the same time.

For now, authorities are focusing on immediate steps: staying hydrated, limiting time outdoors, checking on vulnerable people, heeding fire bans and monitoring official warnings.

But as temperatures climb towards the mid-40s yet again and forecasters reach once more for the Black Summer benchmark, the question hanging over the south-east is not just how communities will endure this week’s heat — but how often they will be asked to endure it in the summers to come.