Climate outlook for July to October
Climate outlook overview
- July to September rainfall is likely to be above median for much of Australia, but below median for south-west Tasmania.
- July to September maximum temperatures are likely to be above median for northern, coastal south-western and far south-eastern parts of Australia, but below median for most other locations.
- Minimum temperatures for July to September are likely to be warmer than median for most of Australia except central WA.
- The likely development of a negative Indian Ocean Dipole, the weakening La Niña, and warmer than average waters around northern Australia are likely to be influencing this outlook.
Above median July to September rainfall likely for most of Australia but drier for south-west Tasmania
- July to September rainfall is likely to be above median for much of Australia (chance of exceeding the median is greater than 60%), with much of the northern and eastern mainland very likely to exceed the median (chances are greater than 80%). However, south-west Tasmania is likely to be below median (chances of exceeding the median are less than 40%).
- Large parts of the eastern two-thirds of mainland Australia (away from the south-east coastline) are around 2 to 4 times more likely than normal to have unusually high (in the top 20% wettest of all past years) rainfall for July to September.
- The July and August outlooks are broadly similar to the three-month outlook, although the chances of above median rainfall are less emphatic. There are roughly equal chances of above or below median monthly rainfall for much of the south-west and south-east during both July and August. July also has a more neutral outlook for the tropical north, while August has a more neutral outlook for most of the rest of WA.
- It should be noted that May to September is the northern Australia 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 much of the remainder
- July to September maximum temperatures are likely to be above median for the northern tropics, coastal south-west 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 a broad area stretching from the Pilbara coast in WA, through northern SA and into southern Queensland and northern and western 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). There is an increased chance of unusually low maximum temperatures (in the bottom 20% of historical records) in a broad area stretching from the Pilbara coast of WA, through most of SA and the southern NT, across the southern half of Queensland, and northern and western NSW (1.5 to 3.0 times the usual chance).
- Minimum temperatures for July to September are likely to be warmer than median for almost all of Australia except central WA (chances greater than 60%), with the eastern two-thirds of the country 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 central WA (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. For minimum temperatures, accuracy is moderate to high across most of Australia, with low to very low accuracy across western parts of WA, and an area in north-west Victoria extending into central SA.
The climate outlook reflects several significant climate influences. These include:
- The Indian Ocean Dipole (IOD). While is currently neutral, the IOD index has been below zero for the past 5 weeks, although mostly weaker than negative IOD thresholds. Outlooks indicate the potential for negative IOD development in the coming months. While IOD outlooks had low accuracy in autumn, the accuracy significantly improves during June. 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 also likely to be contributing to the wetter outlooks and warmer nights forecast for many areas.
- La Niña in the tropical Pacific, which is weakening. Most model outlooks indicate a return to neutral El Niño–Southern Oscillation (ENSO) conditions during winter. However, 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.
- Recent negative values of the Southern Annular Mode (SAM) index. Outlooks after the first week indicate neutral SAM for the following three weeks. A neutral SAM has little influence on Australian climate, while a negative SAM increases the chances of above average rainfall for parts of south-west and south-east Australia.
- Australia's temperature and rainfall variability are also influenced by global warming caused by human activities. Australia's climate has warmed by around 1.47 °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