Australia’s September 2026 was the second-hottest on record, driven by a convergence of global heating and a strengthening El Niño pattern that pushed temperatures 2.71C above the 1961–1990 long-term average. The Bureau of Meteorology (BoM) reported that minimum night-time temperatures reached the highest levels for any September since record-keeping began in 1910. These minimum temperatures were 2.52C above average, surpassing the 2.51C mark set in 2023.
The data reveals a stark trend in continental warming: Australia has not experienced a September with below-average mean temperatures since 2004.
A Continent of Record-Breaking Heat
The warmth was universal. Every state recorded average temperatures within its top five warmest Septembers. In New South Wales alone, 45 locations recorded their warmest Septembers on record.
The impact was most visible in the alpine regions. For the first time since monitoring commenced in 1954, snow depth at the Snowy Hydro monitoring gauge at Spencers Creek in Kosciuszko National Park fell to zero during the month. The BoM confirmed this disappearance was the result of record-breaking September heat combined with warm, rainy winter conditions. In Victoria’s alpine regions, Mount Hotham, Falls Creek, and Mount Buller all saw their hottest maximum temperatures on record for the month. At Thredbo, the average night-time temperature was 0.1C, marking the first time the September daily minimum averaged above freezing, while the town’s hottest September day reached 16C.
El Niño Drives Record Warmth in South-East Australia
The atmospheric catalyst is the ongoing El Niño event in the tropical Pacific. Dr. Simon Grainger, a senior climatologist at the Bureau of Meteorology, attributed the lack of cold days and persistent warmth to high-pressure systems over south-east Australia, intensified by an El Niño projected to be the strongest ever recorded.
Data from the National Oceanic and Atmospheric Administration supports this, showing sea-surface temperatures in the El Niño 3.4 region are currently higher than those recorded during the 2015 event. Readings posted on the Climate Reanalyzer website indicate these temperatures are at record highs, exceeding the 2015 peak about two months earlier. The bureau also noted that August temperatures in oceans between 60°S and 60°N were the warmest on record for any month since 1900, sitting 1.04C above the 1961–1990 average.
This shift is contributing to what Dr. Linden Ashcroft, a climate scientist at the University of Melbourne, calls “seasonal creep”—a phenomenon where winter is ending earlier and spring is starting sooner.
Drought in the East, Deluge in the West
Rainfall patterns were sharply divided. Eastern Australia endured its second-driest September on record, averaging just 8.32 millimetres—down about two-thirds from the long-term norm.
In Tasmania’s north-east, the scarcity was acute. Some areas received less than 10mm of rain, forcing farmers to reduce stock numbers by 20% due to feed shortages. Bruce Dunbabin, owner of Mayfield Estate, said his Swansea farm had dam levels at half when they should be full. BoM senior climatologist Jonathan Pollock stated that Flinders Island and parts of the north-east received less than 20% of their average September rainfall.
Conversely, Western Australia saw its second-wettest September on record and the wettest September since 1904, with rainfall 147% above average. While Perth faced a 95% chance of rain and Darwin dealt with tropical storm activity, Sydney and Canberra remained unseasonably warm, reaching 25C.
South Australian Extremes
South Australia experienced a volatile transition. Adelaide hit 34.4C—the hottest September day in 65 years—before the heat was broken by a cold front that brought thunderstorms and showers. News24 weather presenter Alison Osborne noted that several weather stations in southern South Australia broke all-time heat records on Tuesday. Reprieve arrived Wednesday as showers and thunderstorms spread across the state.
Looking ahead, the bureau released a summary on Thursday stating there is a 60 to 80% chance of below-average rainfall for Tasmania, southern and eastern Victoria, the Cape York Peninsula in Queensland, and northern parts of the Northern Territory’s Top End. For parts of the north and much of eastern Australia, chances of above or below average rainfall for October to December are roughly equal.
While preliminary data for the month has been released, the official climate summary for Tasmania is scheduled for publication on October 5.
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