The rainfall outlook for winter (June to August) 2025 for the South West Land Division indicates that most models suggest a neutral chance of exceeding median rainfall. A neutral outlook means extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible. Temperature outlooks suggest that warmer-than-normal temperatures will persist.
Recent conditions:
• Temperatures remain warmer than normal.
• May rainfall was below average for the South West Land Division (SWLD). A cold front in the last week of May brought rain to the west coast.
• At the time of publication, the autumn break is still yet to occur for some locations in the SWLD.
• The latest Bureau of Meteorology Australian Water Outlook root zone map shows average soil moisture for most of the SWLD, and below average for the south west corner.
Rainfall summary
1 April to 2 June rainfall map shows wetter conditions in the south and drier conditions in the north. DPIRD’s weather station Manjimup has recorded the highest total so far this season with 216 mm.
Southern Annular Mode
The Southern Annular Mode (SAM) is a key climate driver that can influence rainfall and temperature across Australia. SAM refers to the non-seasonal north-south movement of the strong westerly winds that blow almost continuously in the mid- to high-latitudes of the southern hemisphere. This belt of westerly winds is associated with storms and cold fronts that move from west to east, bringing rainfall to southern parts of Australia.
SAM has 3 phases: neutral, positive and negative. Each positive or negative SAM event tends to last for around one to 2 weeks, though longer durations can also occur. The transition between phases is quite random, typically ranging from a week to a few months. SAM has a particularly strong influence on SWLD winter rainfall, with a positive SAM repressing rainfall, and a negative SAM enhancing rainfall.
As of 1 June, SAM is neutral but is forecast to move to a positive phase in the second week of June (unfavourable for rainfall) before returning to neutral until the end of June – indicative of average conditions.
Indian Ocean Dipole
The Indian Ocean Dipole (IOD) is a climate pattern that describes changes in sea surface temperatures (SST) between the western and eastern parts of the Indian Ocean.
In a positive phase, SSTs in the western Indian Ocean are warmer than usual, while waters near Sumatra in the eastern Indian Ocean are cooler, often resulting in reduced rainfall in southern and central parts of Australia. In contrast, a negative IOD occurs when SSTs near Sumatra are warmer and those in the western Indian Ocean are cooler. This shift increases the flow of moisture towards Australia bringing above-average rainfall to southern and central Australia. For the SWLD, a negative IOD typically means average winter-spring rainfall (based on Bureau of Meteorology).
The multi-model seasonal forecast of the SST anomalies from Climate Copernicus for August to October indicates cooler-than-average SSTs in the western Indian Ocean (east of Somalia) and warmer-than-average SSTs in the eastern Indian Ocean (near Sumatra). This pattern is characteristic of a negative Indian Ocean Dipole (IOD) event.
Rainfall outlooks
Three-month and single-month rainfall outlooks are derived from a range of national and international climate models. Outlooks are presented as the probability of rainfall being below, above, or neutral relative to the median rainfall. (Note: A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible). To provide a more localised perspective, the South West Land Division has been divided into two regions, allowing for tailored rainfall outlooks specific to each area.
Rainfall outlooks for the Central West and Central Wheatbelt forecast districts of the South West Land Division
Single month
A summary of 15 national and international models shows that 10 models indicate a neutral chance of exceeding median rainfall for June 2025. A neutral outlook also applies for July and October, with no model consensus for August, September and November. A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible.
Three month
A summary of 18 national and international models shows that 12 models indicate a neutral chance of exceeding median rainfall for winter (June to August). This neutral model consensus also extends to the July to September and August to October periods. A neutral outlook suggests that extreme wet or dry events are less likely, with a wide range of rainfall amounts remaining possible. For spring (September to November), there is currently model consensus for above average rainfall, with 4 out of 6 models that extend this far ahead suggesting wetter conditions. However, it is important to note that forecast reliability decreases with longer lead times.
Rainfall outlooks for the Lower west, South West, Great Southern, South Coastal and South East Coastal forecast districts of the South West Land Division
Single month
A summary of 15 national and international models shows that 10 models indicate a neutral chance of exceeding median rainfall for June 2025. This neutral outlook continues for July through to October, suggesting that extreme wet or dry conditions are less likely, with a wide range of rainfall outcomes remaining possible. For November, the current outlook indicates model consensus for above average rainfall, with 3 out of 4 available models indicating wetter conditions. However, as always, forecast confidence decrease with longer lead times.
Three month
A summary of 18 national and international models shows that 13 models indicate a neutral chance of exceeding median rainfall for winter (June to August). This neutral model consensus also applies for the August to October period. A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible. The current outlook for July to September and spring (September to November) is for above average rainfall. However, it is important to note that forecast reliability decreases with longer lead times.
Important disclaimer
The Chief Executive Officer of the Department of Primary Industries and Regional Development and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.
Copyright © State of Western Australia (Department of Primary Industries and Regional Development), 2025
