Climate outlook for September to December
Climate outlook overview
- Spring (September to November) rainfall is likely to be above median for the eastern two-thirds of Australia, extending into south-east WA. However, below median rainfall is likely for parts of western WA and south-west Tasmania.
- Maximum temperatures for September to November are likely to be above median for the northern tropics and far south-east Australia. Below median daytime temperatures are more likely for other areas of southern Australia extending up into southern Queensland.
- Above median minimum temperatures for September to November are very likely for all of Australia, except southern WA, where the chances of warmer or cooler than median nights are roughly equal, with south-west WA likely to have below median minimum temperatures.
- The negative Indian Ocean Dipole is forecast to continue for spring, and large parts of the eastern tropical Indian Ocean are warmer than average. This can favour above average spring rainfall for parts of Australia. The El Niño–Southern Oscillation is neutral and forecast to remain so, despite cooling of the tropical Pacific likely in the coming months. This cooling may also be increasing the chances of above average spring rainfall for much of eastern and northern Australia.
Above median spring rainfall likely for eastern two-thirds of Australia
- Rainfall for spring (September to November) is likely to be above median for south-east WA, the NT, SA, Queensland, NSW, Victoria and eastern Tasmania (chance of exceeding median is greater than 60%). Much of the eastern States show a greater than 80% chance, as does eastern parts of the NT and SA. Conversely, parts of western WA and south-west Tasmania are likely to have below median rainfall (chance of exceeding the median is less than 40%).
- The pattern for the months of September and October is similar to the spring outlook, though the likelihood of exceeding the median rainfall is not as high in the eastern two-thirds of the country, and extends further west into eastern WA for September.
- Rainfall for October to December is likely to be above median for the eastern half of Australia, and below median for north-west WA.
- Past accuracy for September to November rainfall is high to very high for most of the eastern two-thirds of Australia, with moderate accuracy for central and eastern Victoria, most of WA and the central NT shifting to low accuracy for central areas of WA.
Warmer spring days for the northern tropics and far south-eastern Australia, but cooler for parts of southern and eastern Australia; warmer nights nationwide, except for southern WA
- Maximum temperatures for September to November are likely to be above median for northern tropical Australia, coastal parts of southern NSW and Victoria, and Tasmania (greater than 60% chance), with most of these areas very likely to have warmer September to November days (greater than 80% chance). Below median maximum temperatures are more likely for southern WA, SA, south-east NT, southern Queensland, west of the divide in NSW, and north-west Victoria (chance of exceeding the median is 30 to 40%).
- In September, maximum temperatures are likely to be above median for most of the northern half of Australia, western WA, southern and eastern NSW, south-east SA, Victoria and Tasmania (greater than 60% chance). In October, the warmer pattern retracts, with the far north, and Tasmania likely to be above median, and most of the southern two-thirds of the mainland likely to be below median.
- Minimum temperatures for September to November are very likely to be warmer than median for most of Australia (chances are greater than 80%). However, southern WA has roughly equal chances of above or below median overnight temperatures (chance of exceeding the median is close to 50%), with the south-west more likely to have below median minimum temperatures.
- Likewise, minimum temperatures for September and October are likely to be above median for most areas, with much of southern WA having roughly equal chances of above or below median overnight temperatures. In October, minimum temperatures are likely to be below median for southern WA.
- Past accuracy for September to November maximum temperatures is high to very high for almost all of Australia. For minimum temperatures, accuracy is high across the far north, and most of the southern half of Australia, with moderate to low accuracy for southern WA and central SA, and in a band extending from northern WA, through the central and southern NT and across to central Queensland.
Climate influences
- The negative Indian Ocean Dipole (IOD) event is forecast to continue for the spring months, with a return to neutral IOD in December, which is typical of the IOD seasonal cycle. A negative IOD increases the chance of above average winter–spring rainfall for much of southern and eastern Australia.
- More generally, above average sea surface temperatures to the north of Australia and in the eastern tropical Indian Ocean may also be providing conditions conducive for above average rainfall across some parts of Australia.
- The El Niño–Southern Oscillation (ENSO) is currently neutral. Most climate models indicate cooling of the tropical central Pacific is likely over the coming months, but remain ENSO-neutral. Only one of seven models surveyed by the Bureau indicate this cooling will be sustained enough and cool enough to meet La Niña criteria in spring or early summer, with two other models indicating a brief cooling just to La Niña thresholds. The cooling of the tropical Pacific is likely contributing to the wetter than median outlooks.
- The Southern Annular Mode (SAM) increased in recent days and is forecast to be positive for the next fortnight. A positive SAM typically has a drying influence on south-west and south-east parts of Australia.
- Australia's temperature and rainfall variability are also influenced by global warming caused by human activities. Australia's climate has warmed by around 1.44 °C for the 1910–2019 period, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.
- The Bureau's climate model uses the physics of our atmosphere, oceans, ice, and land surface combined with millions of observations from satellites and on land and sea. As a result, it incorporates the influence of climate change and natural climate drivers like ENSO, IOD, the MJO, and SAM in its outlooks.
Product code: IDCKOATCO2