We are being told to look out for El Niño in the coming months and for it to peak over our summer. But what exactly does that mean?
By Nik Dirga of RNZ
The "climate driver" is likely to bring drier, hotter and windier conditions to much of New Zealand.
In its seasonal climate outlook for June through August, Earth Sciences New Zealand said there's a 95% change of El Niño conditions, an even higher outlook than the United Nations' World Meteorological Organisation, which puts the odds at 80%.
The UN has also issued a warning, telling the rest of the world to be prepared for the extreme heat El Niño may bring.
Here's a quick refresher on what an El Niño season means.
What is El Niño again?
It's when ocean waters off the coast of South America warm above average, and trade winds – the permanent east-west prevailing winds around the Equator – can weaken or sometimes even reverse.
Meteorologists say, given the strength of the climate event, the country will be impacted this winter. (Source: 1News)
It means the sea in the far western Pacific cools down while the eastern Pacific rises.
"Rain and thunderstorms follow the warm ocean water and cool ocean water promotes dryness of high pressure," Earth Sciences NZ principal forecasting scientist Chris Brandolino told RNZ's Nights recently.
That can cause stronger or more frequent winds from the west in summer, and more southerly winds in winter in New Zealand.
"No El Niño is average - each comes with a unique set of climate characteristics and therefore can be expected to influence the weather differently," Earth Sciences NZ notes on its website.
El Niño can be seen as a "climate driver," Brandolino said.
"If you know where your air is coming from you have an idea of what your precipitation or your rainfall patterns are going to be, and your temperature patterns," Brandolino said.
"At a global scale, El Niño events make for warmer years by raising air temperatures and reducing the rate at which the ocean absorbs heat," climate scientist and former Kiwibank New Zealander of the Year Dr Jim Salinger wrote for RNZ recently.
This year's El Niño, Salinger notes, will follow "a rain-soaked start to the year across much of New Zealand, partly owing to the lingering, warm-and-wet influence of El Niño's climate driver counterpart: La Niña".
Explain to me difference between El Niño and La Niña?
If El Niño is hot, La Niña is cool.
The two have typically swapped back and forth every few years in what's known as the El Niño/Southern Oscillation (ENSO).
"They're naturally occurring climate drivers that take place in the Equatorial Pacific, generally," Brandolino said.
La Niña, which is finishing its latest cycle, usually features strong easterly trade winds and cooler waters in the eastern Pacific and warmer waters in the far western Pacific.
In New Zealand, that often means lots of northeasterly winds and moist, rainy conditions to northeastern spots in the North Island. But the lower South Island can, conversely, have less rainfall.
So what does this mean for the coming months?
We're probably going to see less rain and the landslide and flooding events that have hit much of the year so far, but it could also create droughts and heat waves as a result.
"As we move through spring and summer there's a distinct possibility where we could see some pretty hot days," Brandolino told RNZ today.
The rain events that have hit from the north this year are expected to be less frequent.
Earth Sciences NZ's climate outlook states that "rainfall totals for June-August 2026 are about equally likely to be near normal or below normal for the north of the South Island and the west of the North Island".
"Rainfall is most likely to be below normal for the remainder of the North Island, and for the east of the South Island. Meanwhile, rainfall is about equally likely to be near normal or above normal for the west of the South Island."
As for temperatures, Earth Sciences NZ says for the next few months they are most likely to be near average in most places, while it's equally likely that parts of the west side of the South Island would be below average and the east of the South Island below average.
The El Niño patterns are expected to grow stronger, with June seen as a transitional month – the wet weather this past weekend won't be characteristic of the upcoming season, Earth Sciences NZ said.
"Later this winter, this is expected to translate to periods favouring active weather including unusually windy conditions, along with notable temperature variability," Earth Sciences NZ writes in its outlook.
Winter has already started out with some record-breaking high temperatures with nearly 20C seen in Wellington this week.
That lower winter rainfall will have an effect on water-reliant sectors like farmers.
"Some stand-out events – such as in 1982-83, 1997-98 and 2015-16 – caused severe droughts that cost the economy hundreds of millions of dollars," Salinger wrote.
But the impact of El Niño will last longer than the next few months.
"Peak El Niño conditions are expected to occur during the austral summer of 2026-27, with the potential for this event to have significant impacts," Earth Sciences NZ writes.
And what about the rest of the world?
United Nations agency the World Meteorological Organisation issued a statement warning that the risk of extreme weather is high over the coming months.
"The world must treat it as the urgent climate warning it is," UN Secretary-General António Guterres warned.
"El Niño conditions will pour fuel on the fire of a warming world. Impacts will hit even harder, travel even farther, and cross borders with devastating speed."
Brandolino was interviewed at the end of April by RNZ's Nights, and said then that "for the Northern Hemisphere what'll probably happen this summer ... they're going to see some pretty spiky temperatures, some pretty intense temperatures I'm almost certain will make international news."
And that's proven the case, with reports of "mind-boggling" heat in Europe just last week.
"We need to prepare for a potentially strong El Niño event – which will exacerbate drought and heavy rainfall and increase the risk of heatwaves both on land and in the ocean," the WMO's Secretary-General Celese Saulo said.
"The most recent El Niño, in 2023-24, was one of the five strongest on record and it played a role in the record global temperatures we saw in 2024."
Salinger wrote that exactly how this El Niño plays out is still uncertain.
"But coming on the back of the world's warmest period on record, it warrants our close attention."
SHARE ME