A powerful El Niño is forecast to develop over the coming months, with scientists warning it could significantly reshape weather patterns across Aotearoa through winter and into spring.
Earth Sciences New Zealand chief scientist and meteorologist Chris Brandolino says key oceanic and atmospheric signals are aligning, pointing to the rapid emergence of a strong El Niño event in the Pacific.
El Niño is a climate pattern driven by warmer-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. It disrupts normal wind patterns and global circulation, often shifting weather systems far beyond the Pacific. This stands in contrast to La Niña, which is characterised by cooler ocean temperatures in the same region and typically brings more moisture and rainfall to New Zealand’s north and east.
Current observations show clear signs of El Niño building. Sea surface temperatures across the equatorial Pacific are warming steadily, while subsurface ocean heat is rising and spreading eastward — a key early indicator of a strengthening event. At the same time, weakening trade winds and changes in atmospheric pressure patterns are reinforcing the shift, creating the conditions for El Niño to take hold through winter.
For New Zealand, the developing pattern is expected to bring more westerly winds, leading to drier conditions in many eastern regions and increased rainfall in the west. Farmers and rural communities could face heightened risks of dry spells and soil moisture deficits, particularly in areas already vulnerable to drought. While El Niño winters can sometimes be milder overall, the stronger westerly flow also raises the likelihood of sharp cold snaps and frost events, especially in inland and southern areas.
As the system potentially peaks by spring, the implications widen. Agricultural planning, water management, and regional preparedness will all be tested, with a need to balance the risks of dryness in some regions against heavier rainfall and flooding in others. The changing climate pattern may also influence energy demand, crop yields, and fire risk heading into the warmer months.
Communities are being urged to stay informed as forecasts evolve, with the coming months expected to bring a dynamic and, at times, challenging weather outlook.
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