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Seasonal Climate Outlook

October 2025

Summary

Models indicate a neutral chance of exceeding median rainfall for the South West Land Division (SWLD) for the rest of the year (October to December 2025), meaning extreme wet or dry conditions are unlikely, but a wide range of rainfall remains possible. Both day and night time temperatures are expected to be warmer than normal.

Recent conditions:

Nights below 2°C in September were above average, with the Department of Primary Industries and Regional Development (DPIRD) weather station Wickepin North recording the highest number of nights below 2C at 14, 8 above the average. Jingalup was the coldest location with -3.3°C.
September rainfall was above average, with a series of cold fronts bringing consistent rain throughout the SWLD.
After a cool winter (with Badgingarra, Jurien Bay, Cunderdin and Munglingup West recording their lowest winter daily maximum temperatures), temperatures warmed up in September, with DPIRD weather station Gingin West recorded 37.4°C. Harvest is expected to start soon, with reports that swathing of canola has occurred in Dalwallinu.

Rainfall summary

1 April to 31 August rainfall map shows wetter conditions along the coast and drier conditions in the north and central SWLD. Margaret River weather station has recorded the highest rainfall total 1,220 mm. On the other end of the scale, Nungarin weather station has recorded 164 mm since April.

The rainfall decile map for the same period shows decile 8-10 the majority of the SWLD, with Williams and DPIRD Narrogin weather station tracking at decile 1.

Figure 1. Rainfall (mm) totals for 1 April to 29 September 2025 in the SWLD. Margaret River has recorded the highest total of 1,220 mm, Nungarin the lowest with 164 mm.

Figure 2. Rainfall decile ranking map for 1 April to 29 September 2025 for the SWLD, indicating decile 8-9 rainfall for much of the South West Land Division

Temperature risk

During flowering, both low and high temperatures can severely affect crop yield. Minimum temperatures falling below 2°C (frost) and maximum temperatures above 32°C (heat stress) can reduce pollen fertility and grain or pod development (summary in table below). DPIRD creates maps of both frost and heat past and current events to get an idea of risk throughout the SWLD.

Table 1. Summary of frost and heat risk at flowering for cereals and canola.

Number of nights below 2°C (frost risk)

Frost at flowering can affect pollen fertility, grain set and grain size, thereby impacting yield. The number of nights below 2°C provides an indication of frost risk. Number of nights below 2°C (frost severity) maps are generated using data from 332 BOM and 191 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 roughly equivalent to 0°C at ground level, which is cold enough to cause significant damage to cereal crops.

In September 2025, the number of nights below 2°C was generally above the 2000-24 average. For example, the DPIRD weather station Wickepin North recorded 14 nights below 2°C, which is 8 more than the average for that period. Lowest temperature for September was at Jingalup with a minimum temperature of -3.3°C. DPIRD’s extreme weather event tool identifies which DPIRD weather stations have recorded frost potential temperatures based on hourly data.

Figure 3. Number of days below 2°C for 1 - 29 September 2025 for the SWLD. DPIRD’s weather station Wickepin North recorded 14 nights below 2°C.

Figure 4. Average number of nights below 2°C in September for the years 2000-24 for the SWLD. The September 2025 map is greater than these averages.

Cool nights can also occur in October and may cause problems in late-seeded cereals. The average number of nights below 2°C for October (2000-24) shows a reduced spatial extent compared with the September average map, with fewer potential frost events occurring over a smaller area. Wandering BoM weather station has the highest average of nights below 2°C with 4.8 nights. With BoM’s current minimum temperature outlook indicating 45-75% chance of exceeding minimum temperatures for October, frost remains possible in low lying areas.

Figure 5. Average number of nights below 2°C in October for the years 2000-24 for the SWLD. Wandering has the highest average, with 4.8 nights below 2°C.

Number of days above 32°C (heat stress)

The number of days above 32°C provides an indication of heat stress. Temperatures in September 2025, following a very cold July and August, began to rise in late September. Compared with the September average temperatures in the SWLD, September 2025 was warmer than average, with DPIRD station Gingin West recording 37.4°C.

Figure 6. Average September maximum temperatures for Western Australia. In the SWLD, temperatures range from 15°C (in the south west corner) to 24°C (Geraldton).

Figure 7. 1-29 September maximum temperatures for SWLD. Gingin West recorded 37.4°C, higher than the average for September.

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 maps generated utilise rainfall data from 1 April to 22 September and assumes a decile 5 rainfall from 23 September to 31 October, with a WUE values of 15 and 20 kg/ha/mm. The lowest yield potential is 1 – 1.4 t/ha at Nungarin.

Figure 8. Potential yield map, using French and Schultz equation, WUE 15 kg/ha/mm for the SWLD 22 September 2025. Lowest yield potential is for Nungarin at 1t/ha.

Figure 9. Potential yield map, using French and Schultz equation, WUE 20 kg/ha/mm for the SWLD 22 September 2025. Lowest yield potential is for Nungarin at 1.4 t/ha.

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 10. Rainfall outlooks are in 2 sections based on location in the SWLD ̶ first group includes Central West and Central Wheatbelt forecast districts, second group includes 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 models shows that 12 models indicate chances of exceeding median rainfall for October 2025. This neutral model consensus applies for the remainder of the year. A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible.

Figure 11. Single month model summaries for rainfall for the Central West and Central Wheatbelt forecast districts of the SWLD up to December 2025. Model consensus is for neutral chance of exceeding median rainfall for October, November and December.

Three month

A summary of 17 national and international models shows that for the remainder of the year October to December, 10 models indicate neutral chances of exceeding median rainfall. There is also model consensus for neutral chances for November 2025 to January 2026 and summer, December 2025 to February 2026. A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall remains possible.

Figure 12. Model summary of rainfall outlook for the Central West and Central Wheatbelt forecast districts of the SWLD up to summer, December 2025 to February 2026. Model consensus is for neutral chances of exceeding median rainfall.

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 models shows that 8 models indicate chances of exceeding median rainfall for October 2025. This neutral model consensus applies until the end of the year. A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall amounts remains possible.

Figure 13. 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 2025. The majority of models are indicating neutral chance of exceeding median rainfall until the end of the year.

Three month

A summary of 17 national and international models shows that for the remainder of the year October to December, 9 models indicate neutral chances of exceeding median rainfall. There is also model consensus for neutral chances for November 2025 to January 2026 and summer, December 2025 to February 2026. A neutral outlook suggests that extreme wet or dry events are less likely, and a wide range of rainfall remains possible. It is important to note that forecast reliability decreases with longer lead times.

Figure 14. Three month model summaries for rainfall for the Lower West, South West, Great Southern, South Coastal and South East Coastal forecast districts of the SWLD up to summer, December 2025 and February 2026. Model consensus is for neutral chance of exceeding median rainfall.

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.