Climate outlook for July to October
Climate outlook overview
- July to September rainfall is likely to be above median for northern, central and eastern Australia, but below median for western Tasmania and scattered parts of western WA.
- July to September maximum temperatures are likely to be above median for northern, south-western and far south-eastern parts of Australia, but below median for parts of central and eastern Australia.
- Minimum temperatures for July to September are likely to be warmer than median for almost all of Australia.
- The likely development of a negative Indian Ocean Dipole, neutral El Niño–Southern Oscillation during winter, and warmer than average waters around northern Australia are likely to be influencing this outlook.
Wetter July to September likely for northern, central and eastern Australia
- July to September rainfall is likely to be above median for the northern half of Australia, northern and eastern SA, NSW, northern and central Victoria, and eastern Tasmania (chance of exceeding the median is greater than 60%). However, rainfall is likely to be below median in south-west Tasmania and small scattered parts of western WA (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 times more likely than average to have unusually high (in the top 20% wettest of all years over 1981-2018) rainfall for July to September.
- The August outlook is broadly similar to the three-month outlook, although the chances of above median rainfall are slightly less emphatic. However, the July outlook only shows scattered areas of above median rainfall likely across eastern Australia and parts of central Australia, with much of the far south likely to have below median rainfall for the month.
- 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 July to September rainfall is moderate to high for most areas of Australia.
Warmer July to September days likely for north and far south, cooler days for centre and east
- July to September maximum temperatures are likely to be above median for the northern tropics, southern WA, 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 parts of northern SA extending into the southern NT, southern Queensland and nearly all of NSW (chance of exceeding the median is less than 40%).
- There is an increased chance of unusually high maximum temperatures (in the top 20% of historical records) for July to September over the northern tropics, south-west WA, and Tasmania (1.5 to greater than 4.0 times the usual chance).
- Minimum temperatures for July to September are likely to be warmer than median for almost all of Australia except for parts of inland western and south-eastern WA (chances greater than 60%), with northern, central and eastern 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 July to September across almost all of Australia except for much of the southern half of WA and into western SA (1.5 to greater than 4.0 times the usual chance). The highest chance of unusually warm minimum temperatures is across the northern tropics.
- Past accuracy for July to September maximum temperatures is moderate to high for most areas of Australia, and very high for parts of the tropical north. For minimum temperatures, accuracy is moderate to high across most of Australia, with low to very low accuracy across inland western parts of WA, and an area in north-west Victoria extending into central SA; some parts of the tropical north and Tasmania have very high accuracy.
The climate outlook reflects several significant climate influences. These include:
- A potential negative Indian Ocean Dipole. Outlooks indicate a negative IOD is likely to develop in the coming weeks. 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 around northern 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 in the central tropical Pacific during July to September are likely to persist. 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 after the first week indicate neutral to weak positive SAM for 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.
Product code: IDCKOATCO2