Climate outlook for July to October
Climate outlook overview
- July to September is likely to be wetter than average for most of Australia, except western Tasmania and parts of the far north, which are likely to be drier than average. For northern Australia it is now the dry season, which means rainfall totals are typically very low.
- The month of July is likely to be wetter than average across much of mainland southern Australia following a likely drier than average period through June. However, the July outlook does suggest that some parts of the southeast and southwest of the country have equal chances of a wetter or drier than average month.
- July to September days are very likely to be warmer than average across most of Australia, except for SA, eastern WA, southwest NSW and northwestern Victoria, which have roughly equal chances of warmer or cooler winter days.
- July to September nights are very likely to be warmer than average almost nationwide.
- To Australia's east, the central and eastern tropical Pacific Ocean is likely to cool over the winter months, establishing a La Niña-like pattern, while warmer than average waters are likely in the eastern Indian Ocean. In the shorter-term, higher pressure is likely to continue to dominate much of Australia during the second half of June.
Wetter July to September likely for most of Australia
- The fortnight of 15 to 28 June is likely to be drier than average for most of NSW, SA, southern and central Queensland, southern and central NT, eastern Tasmania, and the west coast and northeast of WA (mostly 60–75% chance).
- July to September is likely to be wetter than average for most of WA, SA, NSW, Victoria, the southern half of the NT, and southern Queensland (mostly 65–80% chance). However, western Tasmania and parts of the far north are likely to be drier than average (60–75% chance). Probabilities favouring wetter conditions for July have strengthened following the rapid emergence of a drier pattern in June.
- August to October is likely to be wetter than average for most of eastern and southern mainland Australia. Elsewhere, chances of a wetter or drier August to October are mostly roughly equal.
- Once past June, wetter conditions are established. July to September is likely to be wetter than average for the southern half of Australia (60–70% chance). However, the far southwest and southeast have slightly lower chances.
- May marked the official start of the northern Australian dry season. Tropical northern Australia typically has very low rainfall totals during the dry season, and only a small amount of rainfall is needed to exceed the median.
Warmer July to September days and nights for most of Australia
- A warmer second half of June is likely for most areas, with much of the northern half of WA likely to be 2–4 degrees warmer than usual, and most the NT and southern and central Queensland likely to be 1–3 degrees warmer than usual.
- Days during July to September are very likely to be warmer than average across most of Australia (greater than 80% chance for the tropical north, mostly 60–80% in other parts). However, most of SA, southeast WA, southwest NSW, and western Victoria have roughly equal chances of warmer or cooler days for July to September.
- July to September night-time temperatures are likely to be warmer than average for most of Australia (65–80% chance for southwest WA, Tasmania, and parts of the southeast; greater than 80% chance elsewhere).
Climate influences
- Warmth in the tropical eastern Indian Ocean has eased in recent weeks due to more southerly winds in the east of the basin, and two tropical lows—one of these developed into tropical cyclone Mangga—which brought slightly cooler water to the surface. However, sea surface temperatures remain warmer than average to the northwest of Australia. As a result of these changes, the influence of the Indian Ocean on the Australia's July-September outlook has eased, with some models reducing their chances of a negative Indian Ocean Dipole (IOD) forming during winter.
- The El Niño–Southern Oscillation (ENSO) is likely to remain neutral over winter, though cooling in the central and eastern tropical Pacific is continuing, and a La Niña-like pattern may emerge—though possibly too weak to be declared an event. A minority of models suggest La Niña thresholds may be reached towards the end of winter. The Bureau's ENSO Outlook remains at INACTIVE, but if one more model favours the development of La Niña, the ENSO Outlook will be lifted to La Niña WATCH.
- The Southern Annular Mode (SAM) is forecast to be positive for the next fortnight, with higher pressure likely over Australia during this time. This positive SAM event developed rapidly in early June and is forecast to end during the last week of the month. In winter, a positive SAM typically means less rainfall for southwest WA, southern Victoria, and Tasmania. The positive SAM and higher pressure across Australia are the dominant influences for the outlook for the remainder of June.
- Australia's temperature and rainfall variability are also influenced by global warming caused by human activities. Australia's climate has warmed by around 1.4 °C since 1910, 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 oceans, ice and land surface combined with millions of observations from satellites and on land and sea. As a result, it includes the influence of climate change and natural climate drivers like ENSO, IOD, the MJO and SAM in its outlooks.
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