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Summary
Outlook for October to December is for above median rainfall for the South West Land Division (SWLD). The wetter outlook is partly due to warmer than normal sea surface temperatures in the Indian Ocean, which can provide more moisture to spring and summer weather systems. Both daytime and night-time temperatures are expected to be warmer than normal during spring (September to November 2026) and through to the end of the year (October and December 2026).
Recent conditions
- Rainfall in September was above average for the south west and Great Southern due to a slow-moving low pressure system and surface trough that dragged tropical moisture south, interacting with cold fronts. For the Central West forecast district rainfall was below average.
- September maximum temperatures were above average for the SWLD, with DPIRD weather station Salmon Gums reaching 36.3°C. Minimum temperatures were above average, except at for Wickepin North which had 8 nights below 2°C, which was 2 more than the Septmber average.
- The wetter rainfall outlook for October to December may increase weed burden and allow a green bridge to persist into autumn 2027 (if a wet summer occurs), potentially increasing the carry-over and spread of pests and diseases.
- The El Niño in Pacific Ocean is forecast to persist until autumn 2027. An El Niño over spring/summer can increase bushfire risk, delay the onset of the wet season in northern Australia and reduce the number of tropical cyclones.
Outlook summary
Rainfall summary
Rainfall since April has been variable across the SWLD. The DPIRD weather station at Pemberton has recorded 803 mm of rain, while, in contrast, the Bureau’s weather station at Broomehill has received only 111 mm. The rainfall decile map, which compares this year’s rainfall with the 1975–2025 period, shows the variation in rainfall across the SWLD.
Figure 1. Rainfall (mm) totals for 1 April to 30 September 2026 in the SWLD. Pemberton recorded the highest total of 803 mm and the lowest total is Broomehill with 111 mm.
Figure 2. Rainfall decile map for 1 April to 30 September 2026 in the SWLD, indicating decile 1-3 for half of the SWLD.
Number of nights below 2°C
The number of nights below 2°C provides an indication of frost risk. These maps are generated using data from 332 Bureau of Meteorology and 175 DPIRD stations. Both sets of weather stations measure air temperature in a shaded enclosure (usually a Stevenson Screen) at a height of approximately 1.2 m above the ground. A temperature of 2°C at 1.2 m is equivalent to 0°C at ground level, which is cold enough to cause significant damage to cereal crops.
In September DPIRD weather station Wickepin North had the highest number of nights below 2°C, with 8 which is 2 nights greater than the 2000-25 average. Wandering recorded no nights below 2°C this September, which is 8 nights less than the average.
Figure 3. Difference in the number of nights below 2°C in September 2026 from the 2000-25 average for the SWLD. Quinninup had 4 nights more, while Wandering had 8 nights less than the average.
The average number of nights below 2°C in October (2000-25) indicates that Wandering has the highest number, with an average of 4 nights below 2°C. Despite the outlook for warmer than normal minimum temperatures, frost remains a risk in frost-prone areas. Reduced cloud cover associated with high-pressure systems can increase overnight heat loss, leading to colder surface temperatures and favourable conditions for frost formation.
Figure 4. Average number of nights below 2°C in October for the years 2000-25
Maximum temperature in September
During flowering, high temperatures can severely affect crop yield with high temperatures reducing pollen fertility and grain or pod development. DPIRD weather station at Yuna North East has had 6 days over 30°C in September. The highest temperature recorded in September was at DPIRD weather station at Salmon Gums with 36.3°C.
Figure 5. Maximum temperatures recorded in September 2026 for the SWLD. Salmon Gums recorded 36.3°C.
French and Schultz potential yield
The potential yield map uses seasonal rainfall and decile finishes, calculated from historical data, to determine the maximum possible wheat yield under ideal conditions, without any other constraints, including water logging. This map is a valuable tool in the seasonal decision-making. Potential wheat yield is estimated using the French and Schultz potential yield model, which is expressed as:
Yield (tonnes/ha) = WUE * (stored soil water + growing season rainfall - evaporation)
WUE stands for water use efficiency, and growing season rainfall is measured from April to October. The stored soil water at the start of the growing season is estimated as one-third of the summer rainfall.
The map generated utilise rainfall data from 1 April to 28 September and assumes a decile 5 rainfall from 29 September to 31 October, with a WUE value of 20 kg/ha/mm and evaporation rate of 110 mm. The lowest yield potential is 1.4 t/ha at Pindar South. You can use DPIRD’s potential yield tool to select up to 507 locations and change the WUE and evaporation values in the calculation to suit your farm averages.
Figure 6. Potential yield map using rainfall up to 28 September 2026 with decile 5 finish for October for the SWLD. This map uses French and Shultz calculation using water use efficiency of 20 kg/ha/mm and evaporation of 110 mm. The lowest yield potential is 1.4 t/ha at Pindar South.
Rainfall outlooks
Three-month and single-month rainfall outlooks are derived from a range of national and international climate models. The 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 SWLD has been divided into 2 regions, allowing for tailored rainfall outlooks specific to each area.
Figure 7. Rainfall outlooks are in 2 sections based on location in the SWLD. The first group includes the Central West and Central Wheatbelt forecast districts and the second group includes the Lower West, South West, Great Southern, South Coastal and South East Coastal forecast districts.
Rainfall outlooks for the Central West and Central Wheatbelt forecast districts of the SWLD
Single-month
A summary of 14 national and international climate models shows that 8 models indicate neutral chances of exceeding median rainfall for October 2026. A neutral chance suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible. For November and December 2026 there is model consensus for above median rainfall. Further ahead into 2027 there is model consensus for neutral chances for January and February and no model consensus for March. It is important to note that forecasts are less accurate the further ahead they look.
Figure 8. Single-month model summaries of rainfall outlooks for the Central West and Central Wheatbelt forecast districts of the SWLD up to December 2026. Model consensus is for neutral chances of exceeding median rainfall for October. Note that forecasts are less accurate the further ahead they look.
Figure 9. Single-month model summaries of rainfall outlooks for the Central West and Central Wheatbelt forecast districts of the SWLD up to March 2027. Model consensus is for neutral chances of exceeding median rainfall for January and February. Note that forecasts are less accurate the further ahead they look.
Three-month
A summary of 17 national and international climate models indicates that 11 are indicating above median rainfall for October and December 2027. This model consensus continues for November 2026 to January 2027. For December 2026 to February 2027 there is no model consensus. Note that forecasts are less accurate the further ahead they look.
Figure 10. Three-month model summaries of rainfall outlooks for the Central West and Central Wheatbelt forecast districts of the SWLD up to above median rainfall for October to December 2026 and November 2026 to January 2027. Note that forecasts are less accurate the further ahead they look.
Rainfall outlooks for the Lower West, South West, Great Southern, South Coastal and South East Coastal forecast districts of the SWLD
Single-month
A summary of 14 national and international climate models shows that 10 models indicate neutral chances of exceeding median rainfall for October 2026. A neutral chance suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible. For November and December 2026 there is model consensus for above median rainfall. Further ahead into 2027 there is model consensus for neutral chances for January and February and no model consensus for March. It is important to note that forecasts are less accurate the further ahead they look.
Figure 11. Single-month model summaries of rainfall for the Lower West, South West, Great Southern, South Coastal and South East Coastal forecast districts of the SWLD up to December 2026. Model consensus is for neutral chances of exceeding median rainfall for October. Note that forecasts are less accurate the further ahead they look.
Figure 12. Single-month model summaries of rainfall for the Lower West, South West, Great Southern, South Coastal and South East Coastal forecast districts of the SWLD up to March 2027. Model consensus is for neutral chances of exceeding median rainfall for January and February. Note that forecasts are less accurate the further ahead they look.
Three-month
A summary of 17 national and international models shows that 9 models indicate above median rainfall for October to December 2026. This model consensus continues for November 2026 to January 2027. There is no model consensus for December 2026 to February 2027. Note that forecasts are less accurate the further ahead they look.
Figure 13. Three-month model summaries of rainfall outlooks for the Lower West, South West, Great Southern, South Coastal and South East Coastal forecast districts of the SWLD up to December 2026 to February 2027. Model consensus is for above median rainfall for October to December 2026. Note that forecasts are less accurate the further ahead they look.
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), 2026
