Heat records across the continent

Only one September on record was hotter, with the month's average temperatures coming in 2.71C above the long-term 1961 to 1990 average. Minimums ran 2.52C above average, just beating the 2.51C mark set in 2023. Not since 2004 has the country recorded a September with below-average mean temperatures.

• •Every state placed September among its five warmest, with the Northern Territory sixth hottest
• •45 locations in New South Wales recorded their warmest Septembers on record
• •Overnight minimums were warmer than in any September since national records began in 1910

Alpine snow disappears

Snowy Hydro's monitoring gauge at Spencers Creek in Kosciuszko national park read zero snow depth during September, the first time that has happened in any September since records started in 1954, according to the bureau. At Thredbo, where temperature measurements go back 59 years, the month's average night-time reading was 0.1C - the first time a September's daily minimum has averaged above freezing. The resort's hottest September day reached 16C, about 1C over the previous record set in 2001.

• •Monthly maximum temperatures at Mount Buller, Falls Creek and Mount Hotham in Victoria's alpine regions were all the hottest on record
• •Several alpine weather stations set September records, and many ski resorts closed early after a warm and rainy winter

Warm everywhere, dry in the south-east

"It was pretty much just warm everywhere," said Dr Simon Grainger, a senior climatologist at the bureau. Persistent high-pressure systems over south-east Australia kept days warm and dry, and the sustained lack of cold days through the month stood out as unusual, he said. September was the fourth driest on record for New South Wales and the sixth driest for Victoria. Every state and territory had below-average rainfall except Western Australia, which had its second wettest September on record and its wettest since 1904.

Climate change named the driver

Dr Linden Ashcroft, a climate scientist at the University of Melbourne, said one cause stands clear:

Ashcroft described the pattern as seasonal creep, with winter ending earlier and spring starting sooner. Global heating has warmed the continent by more than 1.5C since country-wide records began in 1910.

Grainger said the El Niño in the tropical Pacific is still intensifying and forecast to be the strongest ever recorded, and likely contributed to September's heat and rainfall patterns.