The Bureau of Meteorology (BoM) has officially declared that a La Niña climate pattern is now active over the Pacific Ocean, setting the stage for a significantly cooler and wetter summer across large parts of Australia for the 2025-26 season.
What La Niña Means for Australian Weather Patterns
This major climate driver, characterised by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific, has a profound influence on global weather. For Australia, its return typically shifts atmospheric conditions, leading to above-average rainfall, particularly across the eastern, northern, and central regions. The bureau's modelling indicates this pattern is likely to persist throughout the coming summer and potentially into early autumn.
Alongside the increased rainfall, La Niña events generally bring cooler daytime temperatures for the southern two-thirds of the continent. However, northern regions may still experience periods of intense heat and humidity. The declaration follows a period of observed oceanic and atmospheric indicators aligning with La Niña thresholds, confirmed in the bureau's climate driver update released on Wednesday.
Increased Flood Risks and a Muted Fire Season
The primary consequence of this shift will be a heightened risk of flooding. Many catchments across eastern Australia are already saturated from recent rains, meaning further precipitation could lead to rapid river rises and flash flooding. Communities are urged to stay informed through official warnings from their local emergency services.
On a more positive note, the forecast wetter conditions are expected to substantially reduce the bushfire risk for the upcoming season, especially in regions like New South Wales and southern Queensland that have faced severe fires in recent years. The increased soil moisture and forecast rain should lead to a less severe grassfire risk in inland areas, though authorities caution that no season is ever completely risk-free.
The last significant La Niña event occurred during the 2020-22 period, contributing to major flooding disasters in parts of eastern Australia. While every event is different, the bureau's senior climatologists have noted the current patterns bear some similarities, warranting a cautious approach from planners and the public.
Long-Term Outlook and Climate Change Context
The BoM's long-range forecast for December 2025 to February 2026 predicts a 70-80% chance of rainfall exceeding the median for most of the country. Maximum temperatures are likely to be below median for much of the south and east, while minimum temperatures could be above average in the north.
This La Niña event unfolds against the ongoing backdrop of human-induced climate change. Scientists note that while natural drivers like La Niña and El Niño still dominate year-to-year variability, climate change is intensifying the water cycle. This can amplify the rainfall associated with La Niña events and contribute to more extreme weather impacts, making preparedness even more critical.
The bureau has committed to monitoring the event closely and will provide regular updates. Residents are advised to use the coming weeks to prepare their properties for heavy rain, review their emergency plans, and stay updated with the latest official forecasts and warnings as the summer season progresses.
