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The pattern ahead sets the stage for the next High Energy Period, focused primarily over the western basin from 8–12 December. Current model guidance indicates Cyclone Genesis near 112–114° E, with the system expected to drift south toward the Pilbara coast by mid-month. Secondary tropical lows are likely to form across the Arafura Sea and near 160° E between Vanuatu and New Caledonia, each forecast to track southeastward.

December marks the transition into early summer, with increasing solar input, warmer surrounding seas and the build-up of the northern wet season. From August through November, rainfall decile patterns have maintained a strong contrast of a drier trend across the south-east and eastern interior, and a wetter to average signal across the north-west and western regions. By averaging the four-month decile trend, December shows a clear continuation of this divide: drier in the s

October 2025 has continued the prevailing theme of below-average rainfall, persistent heat, and inconsistent model performance across much of Australia. Despite sporadic thunderstorm activity and the emergence of a cloud band through the northwest interior late in the month, broad-scale relief has remained elusive. Temperatures have been markedly above average, reinforcing the dominance of high-pressure blocking and limited atmospheric coupling throughout spring.

While mainstream guidance expected a widespread wet spring, OIF’s caution of a drier-leaning start to spring has proven accurate, highlighting the value of including non-traditional drivers beyond ocean indices in seasonal risk assessments.

September long-range review: With a Negative IOD in the background, spring leans drier overall, with coast-favoured rainfall and one major risk window mid-month. We outline climate drivers, temperature signals, and the exact dates most likely to deliver weather of impact, so you can plan works and operations with lead time. Read the full members-only breakdown and weekly refinements through March 2026.

Timing Expectations Primary Window: 18–24 July ↳ NW CBs are climatologically favoured in this period, especially under a -IOD influence Secondary Window: 3–10 July ↳ Should this period not yield widespread NW CB development, attention shifts strongly toward the mid-late month window