El Niño Is Back in 2026: What It Is, Why It Happens, and What It Did Last Time

Every few years the same headline comes round in slightly different words: El Niño is coming, get ready for strange weather. Then it fades again, having explained almost nothing. In 2026 it is back. Forecasters at NOAA, the United States climate agency, and at the World Meteorological Organization expect an El Niño to build through the year and strengthen heading into the winter of 2026-27, possibly reaching a moderate or strong event.

The headline rarely says what the thing actually is. Most people come away with a vague sense that El Niño means bad weather, somewhere, for someone. So here is the thing itself. What El Niño is, why a far-off patch of ocean should steer weather half a world away, what it does when it turns up, and what the last one did only two years ago.

What it actually is

El Niño starts in one particular place: the tropical Pacific Ocean, the huge stretch of water between South America and Asia. It is the biggest single feature on the surface of the planet, and it has an outsized hold on the world's weather. At bottom, El Niño is a change in how that ocean and the air above it behave together.

The change only makes sense next to the normal setup. In a normal year, steady winds called the trade winds blow across the tropical Pacific from the Americas towards Asia. They drag warm surface water westward and pile it up near Indonesia and Australia, so much that the sea there sits a little higher and clearly warmer than the water off South America. As the warm water is pushed west, cold water rises up from the deep along the South American coast to take its place. Warm and wet in the west, cool and dry in the east. That is the system at rest.

El Niño is what happens when the trade winds weaken or reverse. With nothing holding it in the west, the big pool of warm water slides back eastward across the Pacific. The cold water stops rising off South America. A huge stretch of the central and eastern Pacific warms by a degree or two above normal.

A degree or two sounds like nothing, less than the difference between one room and the next. But the tropical Pacific is so big that warming it even slightly moves a vast amount of heat around. Warm ocean makes the air above it rise, and rising air is where storms and rain come from. When the warm water shifts east, the band of rising air and heavy rain shifts with it. The atmosphere is one connected system, so that single move ripples outward and quietly rearranges weather patterns across the whole globe.

Why it keeps happening

El Niño is not a glitch, and it is not a one-off. It is one half of a natural seesaw that scientists call the El Niño-Southern Oscillation, or ENSO. El Niño is the warm phase of that seesaw. The cold phase, when the tropical Pacific runs cooler than usual and the trade winds blow harder than normal, is called La Niña. A neutral state sits between the two, and the system is rarely still for long.

The seesaw tips back and forth on its own, at no fixed pace, roughly every two to seven years. What drives it is a tug of war between the ocean and the winds. The winds shape the ocean, the changed ocean feeds back on the winds, and the two push each other from one phase to the other and back. Nobody switches it on. It is a built-in rhythm of the climate system, one that has been running for thousands of years and shows up in coral records and old ships' logs.

What is new is the setting it now plays out in. ENSO swings the way it always has, but today it does so on top of a planet already warmed by the burning of fossil fuels. The natural cycle has not changed. The baseline underneath it has risen. That is why recent El Niños have managed to push global temperatures to record highs that earlier events of similar size never reached.

What it tends to do

Because El Niño drags the Pacific's warmth and rain eastward, it flips the usual pattern in a great many places at once, often turning wet regions dry and dry regions wet.

The western side of the Pacific, which normally sits under all that piled-up warm water and steady rain, tends to dry out. In practice that often means drought across Indonesia and Australia, and often a weaker monsoon over India. That matters hugely, because hundreds of millions of farmers across South Asia plant and harvest by the timing of that monsoon. On the far side of the ocean, the coast of South America, which is normally dry, can get heavy rain and serious flooding in Peru and Ecuador. It was Peruvian fishermen who gave it its name centuries ago, after noticing that the warm water tended to turn up around Christmas. El Niño means the Christ child.

Its reach goes well beyond the Pacific rim. El Niño tends to:

• Quieten the Atlantic hurricane season while making the Pacific one busier, by changing the high-altitude winds that either tear storms apart or let them grow.
• Change winters across North America, shifting the paths that storms tend to follow.
• Disrupt the fishing off South America. When the cold water stops rising, so does the flow of nutrients that feeds the huge shoals of anchovy, and the fishery, one of the biggest on Earth, can collapse for a season.
• Put stress on the world's coral reefs, which bleach and can die when the water around them stays too hot for too long.

And one effect reaches everyone, everywhere. El Niño lets heat that had been stored in the ocean escape up into the air, and that gives a temporary lift to the average temperature of the whole planet. In a year with a strong El Niño, the whole world simply runs hotter.

What the last one did

None of this has to be imagined, because the last El Niño was recent and severe. It built through the second half of 2023, was rated a strong event, and finally faded in May 2024.

While it lasted, it stacked its natural warmth on top of the long-term warming from climate change, and the two added together to help make the stretch from mid-2023 into 2024 the hottest ever measured. The oceans set new heat records month after month, for so many months in a row that scientists said openly that the numbers unnerved them.

That ocean heat had effects you could see. It drove the fourth global coral bleaching event, which researchers have called the most widespread and intense ever recorded, hitting reefs from the Caribbean to the Maldives to the wider Pacific. On land, the same pattern helped push the Amazon into a severe drought that dropped some of its rivers to their lowest levels on record, cutting off riverside communities that rely on the water to get around and to eat. It dried out Central America badly enough that water levels in the Panama Canal fell, forcing the authorities to cut the number of ships allowed through and slowing part of global trade. Parts of Africa swung hard between flooding and drought.

It was not just a curiosity for weather buffs. It reshaped harvests, shipping lanes, coral reefs, and record books, all inside a single turn of the seesaw.

Why 2026 matters

On its own, an El Niño is a natural swing that the planet has always ridden out, over and over, for as long as there has been a Pacific Ocean. That is not the worry. Forecasters are watching the 2026 event so closely because of the ground it is landing on.

The 2026 El Niño will build on top of a climate that is already the warmest in the instrumental record. When the natural warm phase lands on that raised baseline, the two add together. The odds of new global temperature records go up, and so does the risk of the extremes a warm phase tends to bring: heatwaves that turn dangerous, monsoons that show up weak and leave fields dry, hurricane seasons shifted around, reefs pushed past the temperature they can survive.

El Niño is not the whole story. It turns up the odds of a hotter, more disrupted year on a planet where those odds already start higher than they used to.

When the El Niño headlines come back through 2026, this is what they are pointing at. It is not a single storm or one disaster with a name and a date. It is a shift in one huge patch of the Pacific that quietly tilts the year towards heat and disruption, for a great many people who will live through the results without ever hearing the phrase trade winds.

Sources

• NOAA, "El Niño forms, expected to strengthen, say NOAA forecasters".
• World Meteorological Organization, "El Niño is forecast to intensify, increasing likelihood of extreme weather".
• NASA Earth Observatory, "El Niño Exits" (on the 2023-24 event's impacts).
• Wikipedia, "2023-2024 El Niño event".