Climate outlook for September to December
Long-range forecast overview
- For September to November, below median rainfall is likely to very likely (60% to greater than 80% chance) for most of Australia.
- For September to November, above median maximum temperatures are very likely (greater than 80% chance) for almost all of Australia.
- For September to November, warmer than median minimum temperatures are likely (60 to 80% chance) to very likely for most of western and southern Australia.
- The long-range forecast is influenced by several factors, including likely El Niño development and positive Indian Ocean Dipole development, and record warm oceans globally.
Drier than median spring for most of Australia
- For September, below median rainfall is likely to very likely (60% to greater than 80% chance) for most of Australia, excluding the NSW coast and northern Queensland.
- For September to November, below median rainfall is likely (60 to 80% chance) for southern WA and most of the eastern two-thirds of Australia. Chances of below median rainfall increase to very likely (greater than 80% chance) for areas of southern Australia and eastern Queensland.
- Unusually low rainfall is at least 2 times as likely for much of southern Australia and broad areas of the NT and Queensland. Unusually low rainfall equates to the driest 20% of September to November periods from 1981 to 2018.
- Past accuracy of September to November long-range forecasts for the chance of above median rainfall is high to very high for most of Australia, decreasing to low to very low for some western areas of the mainland.
Warmer than median days and nights for most of Australia during spring
- For September, above median maximum temperatures are likely to very likely (60% to greater than 80% chance) across the southern two-thirds of Australia. Below median maximum temperatures are likely (60 to 80% chance) for the Queensland Gulf Country, and central and eastern NT.
- For September to November, above median maximum temperatures are very likely (greater than 80% chance) for almost all of Australia.
- For September to November, most of Australia is at least 2.5 times as likely to experience unusually high maximum temperatures (unusually high maximum temperatures equates to the warmest 20% of September to November periods from 1981 to 2018), with chances increasing to more than four times as likely for most of western and central WA and parts of the southeast.
- For September, above median minimum temperatures are likely to very likely (60% to greater than 80% chance) for Tasmania, Victoria, NSW on and east of the Great Dividing Range, the Southeast Coast of Queensland, and most of WA. Below median minimum temperatures are likely to very likely across most of the NT, the Kimberley and Northern Interior regions of WA, central and western Queensland, the far west of NSW and the North East Pastoral and Flinders districts of SA.
- For September to November, minimum temperatures are likely (60 to 80% chance) to be warmer than median for most of Australia excluding areas of north-east NT, northern Queensland, and south-east SA. Chances increase to very likely (greater than 80% chance) for Western Australia and parts of eastern Australia.
- For September to November, western and central areas of WA and areas on and east of the Great Dividing Range in NSW and Victoria are at least 3 times as likely to experience unusually high minimum temperatures (unusually high minimum temperatures equates to the warmest 20% of September to November periods from 1981 to 2018), with chances increasing to more than four times as likely for parts of central WA.
- Past accuracy of the September to November chance of above median maximum and minimum temperature long-range forecasts has been high to very high across all of Australia.
Climate influences
The long-range forecast reflects known impacts from several significant climate drivers:
- The El Niño–Southern Oscillation (ENSO) outlook remains at El Niño Alert. In the past, when we have reached El Niño Alert, events have subsequently developed around 70% of the time. El Niño typically increases the chance of below average spring rainfall for the eastern half of Australia, and above average daytime temperatures for the southern two-thirds of Australia.
- Climate models suggest a positive Indian Ocean Dipole (IOD) is likely in spring. The last two weeks have seen the Indian Ocean Dipole (IOD) index above the positive IOD threshold of +0.40 °C. However, several more weeks of positive IOD values are needed to have more confidence on whether a positive IOD event is emerging. A positive IOD typically decreases spring rainfall for much of Australia.
- The Southern Annular Mode (SAM) index is currently neutral and is expected to become slightly negative and then return to neutral during September.
- Longer-term trends: Australia's climate has warmed by around 1.47 °C in the period from 1910 to 2021, leading to an increased frequency of extreme heat events. Southern Australia has seen a 10 to 20% reduction in cool season (April to October) rainfall in recent decades.
The Bureau's climate model simulates the physics of atmospheric, oceanic, ice, and land surface processes and uses millions of observations from satellites as well as in-situ instrumentation on land and at sea. These simulations enable the model to account for the influence of climate change and natural climate drivers like ENSO, IOD, the Madden–Julian Oscillation (MJO) and SAM in its long-range forecasts.
Product code: IDCKOATCO2