The U.S. Climate Prediction Center has declared the onset of La Niña, a weather phenomenon expected to influence global weather patterns through early 2026. For Australia, this could mean increased cloud cover, rainfall, and cooler temperatures, particularly in the country’s northern and eastern regions. However, experts caution that this La Niña may be weak and brief, with other climate drivers likely to play a more significant role.
Understanding La Niña: A Brief Overview
La Niña is part of the El Niño-Southern Oscillation (ENSO) cycle, which also includes El Niño and neutral phases. The phenomenon is characterised by cooler-than-average sea temperatures in the central and eastern Pacific Ocean. These cooler temperatures, in turn, strengthen easterly trade winds and shift atmospheric pressure patterns, often resulting in increased rainfall in some areas and droughts in others.
La Niña’s impact on weather is usually most evident during late spring and early summer in the Southern Hemisphere. According to Weatherzone, moderate-to-strong La Niña events can lead to enhanced cloud cover and rainfall, while also suppressing daytime temperatures over large areas of Australia. This effect is particularly felt in northern, central, and eastern regions, where higher-than-average rainfall and cooler temperatures are common. However, this event is expected to be weak and short-lived, potentially limiting its impact.
A Weaker La Niña This Year
The latest advisory from the U.S. Climate Prediction Center suggests that La Niña conditions are likely to persist through December 2025, with a transition to neutral conditions expected by early 2026. However, the Bureau of Meteorology (BOM) in Australia has yet to officially declare La Niña, as it has not met the stricter thresholds they apply. While the CPC’s criteria for La Niña include a sustained drop of at least 0.5°C in sea surface temperatures, the BOM requires a more prolonged cooling before making an official declaration.
Experts agree that while the current La Niña-like conditions have been observed in the Pacific Ocean, their expected weakness and short duration mean they may not have as significant an effect on Australian weather as initially feared. Instead, other climate factors—such as the Indian Ocean Dipole (IOD) and abnormally warm sea surface temperatures closer to Australia—are expected to exert a greater influence on the climate in the coming months.
In the broader context, La Niña is just one of several climate drivers influencing weather patterns in Australia. The warming of the oceans, accelerated by climate change, is complicating the predictions for both La Niña and its counterpart, El Niño. The Bureau of Meteorology has recently revised its approach to understanding these patterns, factoring in the ongoing effects of global warming.
