El Niño Roars Back: One of the Strongest Events in Recent History Set to Shape Aotearoa’s Spring

El Niño conditions across the tropical Pacific atmosphere and ocean have strengthened considerably since mid-winter, with their influence on New Zealand’s weather patterns now beginning to emerge.

The latest outlook indicates the event could reach the very strong category as early as September, before reaching its peak during late spring or early summer.

Of particular significance is the rate at which the Pacific is changing. The developing event is already comparable with 1997, while its warming trend is described as the strongest on record.

That raises the prospect of a significant climate event influencing Aotearoa through the crucial spring and early summer period.

What El Niño means for Aotearoa

El Niño does not mean every day will be hot or dry.

Instead, it changes the large-scale atmospheric patterns influencing New Zealand’s weather.

For spring 2026, that is expected to favour periods of stronger and more active westerly winds, unusually windy conditions and greater fluctuations in temperature.

While changeable weather and strong winds are normal features of a New Zealand spring, those characteristics are expected to become more pronounced this year.

The positioning of high-pressure systems around the country will determine exactly how persistent those conditions become, but the greatest risk of widespread unsettled weather is currently expected during mid-to-late spring.

Occasional cold outbreaks are also expected despite the overall seasonal outlook favouring average or warmer temperatures across much of the country.

North and east face a drier spring

The rainfall outlook demonstrates how differently El Niño can affect regions across the motu.

For the north and east of the North Island, rainfall during September to November is most likely to be below normal.

The west of the North Island and north and east of the South Island are about equally likely to experience near-normal or below-normal rainfall.

That could become increasingly important as spring progresses, particularly if prolonged dry periods begin reducing soil moisture and river levels heading towards summer.

For farmers, growers, iwi, hapū and communities dependent on freshwater supplies, the combination of reduced rainfall and warmer conditions will be closely watched.

West Coast faces the opposite problem

While parts of the country could become increasingly dry, the west of the South Island faces almost the opposite outlook.

Rainfall there is considered very likely to be above normal through spring.

That reflects the stronger westerly weather patterns associated with El Niño, which can drive moisture-laden air onto the western side of the Southern Alps.

It means Aotearoa could simultaneously be dealing with drying conditions in northern and eastern regions while western areas experience repeated heavy rainfall.

That regional contrast is one of the defining characteristics of El Niño’s influence on New Zealand.

Warmer north and east

Temperatures are also expected to vary considerably around the country.

Seasonal temperatures are most likely to be above average across the east and north of the North Island.

The west of the North Island and north and east of the South Island are expected to experience near-average or above-average temperatures.

The west of the South Island is most likely to remain around average.

But seasonal averages can hide short-term extremes.

Cold southerly outbreaks remain possible throughout spring, meaning whānau could experience periods of unusually warm weather followed by sharp temperature drops.

Awa and whenua could feel the pressure

Soil moisture and river flows provide another important warning.

For the east and north of both islands, west of the North Island and north of the South Island, soil moisture levels and river flows are expected to be near normal or below normal during spring.

In western parts of the South Island, they are expected to be near normal or above normal.

For tangata whenua, those changes are about much more than the weather.

Reduced river flows and drying whenua can affect mahinga kai, indigenous freshwater species, wetlands, farming, horticulture and the health of awa and roto.

That comes as conservation organisations are already warning of serious pressure on Aotearoa’s indigenous biodiversity and freshwater ecosystems.

A strong El Niño could add another stressor to species and habitats already confronting water quality decline, habitat loss, introduced predators and climate change.

Drought and wildfire risk will be watched

The possibility of prolonged dry conditions will also turn attention towards drought and wildfire risk.

If northern and eastern regions experience extended periods of below-normal rainfall alongside warmer temperatures and strong winds, vegetation and soils can dry rapidly.

That combination can increase fire danger and place additional pressure on rural water supplies.

For Māori communities, the implications can extend from farms and whenua Māori to marae water security and culturally significant ecosystems.

The experience of previous extreme weather events has also demonstrated that isolated and rural communities can be disproportionately affected when roads, water systems or other infrastructure come under pressure.

A powerful Pacific climate event

El Niño develops when the tropical Pacific ocean and atmosphere undergo significant changes, including warming of ocean waters across the central and eastern equatorial Pacific.

This year’s event is attracting particular attention because warmer-than-average temperatures beneath the ocean surface have continued to strengthen and expand.

That subsurface warmth provides further energy capable of sustaining and intensifying El Niño.

Current indications suggest the event could reach its maximum strength in late spring or early summer, placing its peak close to the period when Aotearoa begins moving into the hottest and often driest part of the year.

Prepare for extremes, not one weather pattern

The important message for whānau is that a powerful El Niño does not produce one uniform outcome across New Zealand.

Some regions could become drier.

Others could become considerably wetter.

Strong westerlies could create damaging wind events, while periods of warmth could still be interrupted by cold outbreaks.

River flows and soil moisture could decline across large parts of the north and east while western Te Waipounamu receives substantially more rain.

That variability means communities, councils, farmers, emergency services and infrastructure operators will need to watch regional forecasts closely rather than relying solely on the national seasonal picture.

Earth Sciences New Zealand is launching a live El Niño Strength Tracker from 2 September, allowing the public to follow the development of the event as conditions evolve.

The developing El Niño is already comparable with one of the strongest historical events and has recorded an exceptional warming trend.

For Aotearoa, the message heading into spring is increasingly clear: expect more wind, greater weather variability and potentially significant differences between a drying north and east and a wetter western South Island.

And with El Niño still strengthening, its biggest impacts may yet be ahead of us.

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