Weather watch: shifting rainfall trends across Australia
Key points
- Southern Australia is experiencing a long-term decline in cool season rainfall, particularly in the southwest and southeast.
- Northern Australia has become wetter over the past 30 years, especially during the wet season.
- From October to December, eastern Australia is likely to see above average rainfall.
Australia’s weather systems are shifting, with rainfall patterns differing between the continent’s north and south. In southern Australia the cooler months (April to October) are critical for rainfall, as this period supports crop growth, streamflow, and groundwater recharge. However, in recent decades, particularly across the southwest and southeast, cool season rainfall has declined. In these regions, low-pressure systems and cold fronts are becoming less common and less effective. This drying trend represents the most sustained large scale change in southern rainfall since records began in the late 1800s.
Australian rainfall is highly variable and is strongly influenced by seasonal climate influences such as El Niño, La Niña, the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). Despite this natural variability, long-term trends are evident in Australia’s rainfall records. More recently, there’s been a shift towards drier conditions across the southwest and southeast of Australia, with more frequent periods of below average rainfall, especially for the cool season months.
In southwest WA, average rainfall from May to July has been around 20% lower since 1970 compared with records between 1900–1969. Cool season rainfall declined by around 16% over the same period. The trend has intensified over the last 30 years, with May to July average rainfall declining around 24% since 1994, despite relatively high rainfall in 2021. It is highly unlikely that a decline of this magnitude could have occurred due to natural variability alone.
In contrast, northern Australia has become wetter over the past 30 years, particularly during the wet season (October to April). Rainfall across the north has been around 20% above the long-term average. Several of the wettest seasons on record have occurred since the late 1990s. Significant rainfall increases have been seen in the northwest but variability remains high. The last decade has been closer to long-term averages compared to the wetter periods of the late 1990s and early 2010s. Meanwhile, parts of eastern Queensland, south of the tropics, have shown a drying trend over the past decade, with lower rainfall throughout the year.
From October to December, rainfall is expected to be above average across much of eastern Australia, with a 60−80% chance of wetter conditions and the strongest signal over Cape York Peninsula.
The forecast is less certain for the rest of the country. Producers should remain flexible, monitoring local conditions closely and preparing for both dry and wet scenarios. As northern Australia transitions into the wet season during October and November, increasing humidity, storms and showers are expected to become more frequent, marking the typical onset of seasonal rainfall in the tropics.
Attribute content to Emily Tan, MLA Market Information Analyst
Information is correct at time of publishing on 1 October 2025
