Lethal Heating: 12/05/25

Key Points

Australia has already warmed by about 1.5 degrees above pre‑industrial levels, driving harsher heat, fire weather and ocean extremes.¹
The Bureau of Meteorology expects warmer than average days and nights across most of Australia this summer, with an elevated risk of extreme heat.²
Climate change is altering rainfall patterns, amplifying both long dry spells and short, intense downpours that heighten flood risk.³
Longer fire seasons and higher bushfire risk are emerging across large areas of southern and eastern Australia as conditions become hotter and drier.⁴
Hotter oceans and more frequent marine heatwaves are reshaping Australia’s weather patterns and putting additional stress on coasts and reefs.⁵
Scientists say the fingerprint of human‑driven climate change can now be seen in many of Australia’s recent extreme weather events.⁶

Australia’s Summer Turns Up the Heat as Climate Shift Bites

Australia is heading into another hotter than average summer, as a rapidly warming climate reshapes the nation’s weather and raises the stakes for heatwaves, bushfires and floods.¹

New assessments from the Bureau of Meteorology and CSIRO show Australia has already warmed by about 1.5 degrees above pre‑industrial levels, a threshold many global agreements framed as a line not to be crossed.¹

This extra heat is loading the dice towards longer and more intense heatwaves, longer fire seasons, and heavier bursts of rain when storms do break through.³

The Bureau’s latest long‑range outlook points strongly to warmer than average days and nights across most of the continent this summer.

There is an increased risk of extreme heat and elevated bushfire danger in parts of New South Wales, Victoria and Western Australia.²

Rainfall is likely to be below average in western and inland eastern regions.

Much of the east coast and southern states face a coin toss between drier or wetter than normal conditions, complicating preparation for heat, fire and flood risks.²

Scientists say these patterns are not random swings of natural variability but consistent with a climate pushed into new territory by decades of greenhouse gas emissions.¹

From the Black Summer fires to recent coastal flooding and marine heatwaves, many of Australia’s most damaging recent events now carry a clear climate change fingerprint, even as year‑to‑year drivers like El Niño and La Niña still shape each season’s flavour.⁶

The result is a summer outlook where old rules of thumb no longer hold, and the line between ordinary bad weather and climate‑charged extremes is rapidly eroding.³

Climate change and a hotter Australia

The latest State of the Climate report from CSIRO and the Bureau of Meteorology finds Australia’s land area has warmed by 1.51 degrees since 1910, with the most rapid warming occurring since 1950.¹

This warming has already led to more extreme heat events, fewer cold extremes, and a marked increase in the number of days with dangerous fire weather in many regions.¹

Heatwaves are becoming longer, hotter and more frequent, and health data show that extreme heat remains Australia’s deadliest natural hazard, exceeding deaths from floods, storms and bushfires over recent decades.⁶

The report also concludes that these trends will continue as long as greenhouse gas concentrations rise, locking in more years where record‑breaking heat is more likely than cool relief.¹

Changing rainfall and storm patterns

Climate change is not only raising temperatures, it is altering the way rain falls across the continent, deepening some drought risks while intensifying downpours when moisture does arrive.³

Since the 1970s, cool‑season rainfall has dropped by around 16 per cent in south‑west Western Australia and about 9 per cent in parts of south‑east and eastern Australia, trends that have reduced streamflows and stressed water supplies.³

At the same time, northern Australia has seen roughly a 20 per cent increase in wet‑season rainfall compared with 30 years ago, contributing to more frequent and severe flooding in some tropical catchments.³

Across many regions, more of the rain is falling in short, intense bursts, increasing the risk that urban drains and river systems will be overwhelmed and that flash flooding will hit with little warning.³

Fire seasons stretched by heat and fuel

Warmer temperatures, shifting rainfall and lower humidity are combining to lengthen Australia’s fire seasons and increase the frequency of days with dangerous fire weather, particularly in southern and eastern states.⁴

Recent assessments show that large areas of eastern Australia are now experiencing more high fire danger days than in the late 20th century, with climate change a major driver of this trend.⁴

In grassland and savanna regions, periods of heavy rain can produce explosive fuel growth that later dries out in hot conditions, priming the landscape for fast‑moving grassfires and broad‑scale burns.⁴

The harsh Black Summer fires of 2019–20 have been linked by multiple studies to the background warming trend and record‑dry conditions, showing how climate change can amplify natural drivers like drought and modes of ocean variability.⁶

Oceans, marine heatwaves and coastal risks

Australia’s surrounding oceans are warming fast, with the State of the Climate report noting that most of the extra heat trapped by greenhouse gases is being absorbed by the seas.⁵

Marine heatwaves, periods when sea temperatures remain unusually high for days to months, are becoming more frequent and intense, stressing coral reefs, kelp forests and fisheries from the Great Barrier Reef to southern coasts.⁵

Sea levels around Australia are rising in line with the global trend, increasing the likelihood that storm surges and high tides will combine with heavy rain to cause damaging coastal flooding in low‑lying suburbs and towns.⁵

These changing ocean conditions also feed back into weather patterns by influencing moisture availability, storm formation and the behaviour of large‑scale climate drivers that help set up Australia’s wet and dry cycles.⁵

Summer 2025–26 outlook: hotter, drier in many regions

The Bureau of Meteorology’s long‑range forecast for December 2025 to February 2026 shows a strong likelihood of above‑average temperatures across almost the entire continent, for both daytime maxima and night‑time minima.²

Forecasters flag an increased risk of extreme heat during the summer, meaning more days and nights where high temperatures persist and limit the chance for people, infrastructure and ecosystems to cool down.²

Rainfall is likely to be below average for parts of western Australia and inland eastern districts, while much of the east coast and southern states show no strong signal either way, leaving communities to prepare for both dry and stormy spells.²

The Bureau notes that its outlook explicitly incorporates both short‑term climate drivers and the long‑term warming trend, underscoring how climate change is now baked into every seasonal forecast rather than sitting in the background.²

These projections translate into heightened bushfire risk for parts of New South Wales, Victoria and Western Australia, particularly where heavy vegetation growth in recent years has left high fuel loads that will dry out rapidly in heat.²

Are recent extremes linked to climate change?

Attribution studies, which investigate how much climate change influences specific events, now conclude that many recent Australian heatwaves and fire seasons would have been far less likely without human‑driven warming.⁶

Scientists highlight that while natural patterns such as El Niño, La Niña and the Indian Ocean Dipole still shape year‑to‑year variability, climate change is effectively shifting the baseline so that these patterns play out on a hotter, more energy‑loaded planet.⁶

The State of the Climate report states that harsher fire weather, more marine heatwaves, longer fire seasons and more intense downpours are all consistent with what climate models have long projected for a warming Australia.¹

This means that the question for many recent extremes is no longer whether climate change played a role, but how much it increased their likelihood and severity compared with a world without elevated greenhouse gas levels.⁶

What this means for an Australian summer

For households, the evolving climate means preparing for longer stretches of heat, paying closer attention to heat health advice, and treating bushfire warnings and flood alerts as signals that can no longer be safely ignored.⁶

For emergency services and planners, it means that summer is increasingly a season of overlapping risks, with hot, dry weeks that elevate fire danger punctuated by sudden storm outbreaks that can unleash flash floods on saturated or fire‑scarred catchments.³

For governments, the scientific advice is that cutting emissions sharply remains essential to limit further warming, while investment in adaptation, from heat‑ready housing to resilient infrastructure and early warning systems, has become an urgent necessity rather than a distant goal.¹

References

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05/12/2025

Heat, Fire, Flood: Climate Change Drives a New Australian Summer - Lethal Heating Editor BDA