Climate outlook for August to November

Climate outlook overview

• August to October rainfall is likely to be above median for the eastern two-thirds of Australia, but below median rainfall likely for western Tasmania.
• August to October maximum temperatures are likely to be above median for northern, and parts of far southern Australia, but below median for parts of eastern Australia.
• Minimum temperatures for August to October are likely to be warmer than median almost Australia wide.
• A developing negative Indian Ocean Dipole, along with warmer than average waters around northern Australia, and neutral phase of the El Niño–Southern Oscillation during winter, are likely to be influencing this outlook.

Wetter August to October likely for most of eastern two-thirds of Australia 

• August to October rainfall is likely to be above median for far eastern parts of WA, the NT, SA, Queensland, NSW, Victoria, and eastern Tasmania (chance of exceeding the median is greater than 60%), with much of the eastern half of the country very likely to be above median (greater than 80% chance). However, rainfall is likely to be below median in western Tasmania (chances of exceeding the median are less than 40%).
• Large parts of northern, central, and eastern mainland Australia (away from the southern coastline) are around 2 to 3.5 times more likely than average to have unusually high (in the top 20% wettest of all August–October periods over 1981–2018) rainfall for August to October.
• The August and September monthly outlooks are broadly similar to the three-month outlook, although the chances of above median rainfall are slightly less emphatic. August has slightly more widespread chances of wetter conditions into central WA, and a more neutral outlook for northern Australia.  
• It should be noted that May to September is the northern Australian dry season. This means tropical northern Australia typically has very low rainfall totals during this time (large areas less than 25 mm for the season), and only a small amount of rainfall is needed to exceed the median.
• Past accuracy for August to October rainfall is moderate to high for most areas of Australia, but low for inland southern and central WA.

Warmer August to October days likely for north and far south, cooler days for east

• August to October maximum temperatures are likely to be above median for the northern tropics, south-western Australia, far south-east SA, southern and north-eastern Victoria extending into south-east NSW, and Tasmania (greater than 60% chance). Below median maximum temperatures are likely for the south-eastern quarter of Queensland and much of the eastern half of NSW (chance of exceeding the median is less than 40%).
• There is an increased chance of unusually high maximum temperatures (in the warm 20% relative to the 1981–2018 period) for August to October over the northern tropics, south-west WA, far south-east SA, south-west Victoria and Tasmania (1.5 to greater than 4.0 times the usual chance).
• Minimum temperatures for August to October are likely to be warmer than Australia wide (chances greater than 60%), with most of the eastern two-thirds of Australia very likely to be warmer than median (chances are greater than 80%).
• There is an increased chance of unusually high minimum temperatures (in the top 20% of historical records) for August to October across almost all of Australia (1.5 to greater than 4.0 times the usual chance). The highest chance of unusually warm minimum temperatures is across the northern tropics and Tasmania.
• Past accuracy for August to October maximum temperatures is high to very high for most areas of Australia. For minimum temperatures, accuracy is moderate to high across most of Australia; some parts of the tropical north, Australia's eastern coastline, and Tasmania have very high accuracy.  

Climate influences

The climate outlook reflects several significant climate influences. These include:

• The likely development of a negative Indian Ocean Dipole. Outlooks indicate a negative IOD event is likely for the coming months. A negative IOD increases the chances of above average winter–spring rainfall for large parts of Australia. It also increases the chances of warmer days and nights for northern Australia.
• Above average sea-surface temperatures, particularly to the north of Australia. These are likely to be contributing to the wetter outlooks and warmer nights forecast for many areas.
• The recent end of the La Niña in the tropical Pacific, and shift to La Niña WATCH. Most model outlooks indicate neutral El Niño–Southern Oscillation (ENSO) conditions during winter. However, slightly cooler than average sea-surface temperatures are likely to persist in the central tropical Pacific for the remainder of winter. This, combined with warmer ocean temperatures in the western tropical Pacific, would favour average to above average winter rainfall for eastern Australia. In the longer term, around half the models surveyed favour a return to La Niña during spring.
• The Southern Annular Mode (SAM). Outlooks for the SAM currently show some volatility in the first week, and trending towards a neutral SAM in the following three weeks. A neutral SAM has little influence on Australian climate.
• Australia's temperature and rainfall variability are also influenced by global warming caused by human activities. Australia's climate has warmed by around 1.47 °C for the 1910–2020 period. Southern Australia has seen a reduction of 10% to 20% in cool season (April–October) rainfall in recent decades. There has also been a trend towards a greater proportion of rainfall from high intensity short duration rainfall events, especially across northern Australia.

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.