El Niño is the planet’s naturally recurring chaos agent, scrambling weather patterns, spiking global temperatures and typically reaching full strength by December. It appears at irregular intervals, and no two events are the same. Scientists measure its magnitude by how far temperatures in the Pacific Ocean rise beyond the norm, but don’t think you have to live near the Pacific to experience El Niño: This year’s event is predicted to be the strongest ever recorded, and its effects will be global.
What Is El Niño?
El Niño is a natural climate pattern that recurs every few years. It typically develops in spring or summer, intensifies through autumn and peaks over the winter.
It is not a storm in itself, but rather the atmospheric scaffold upon which global weather is built. An El Niño does not guarantee a soaked California winter or a mild Christmas in New York City, but it tilts the odds heavily in favor of that happening.
Think of El Niño as a dance between the ocean and the atmosphere. As winds in the tropical Pacific weaken, warm water that would have ordinarily been forced to stay near Indonesia instead sloshes east, dragging the ocean’s primary zone of thunderstorm activity with it. This shift acts like a boulder dropped into a stream, rippling up through the atmosphere to disrupt weather patterns worldwide.
Why is this El Niño getting so much attention?
Primarily, because of its record-breaking scale. And because it comes after several decades of hard-hitting events that increased awareness about this phenomenon.
A devastating El Niño in the winter of 1982-83 killed thousands worldwide. The disaster set off two efforts, one inside the United States and one internationally, to fund and build an observational network capable of forecasting future El Niños. By the mid-1990s, scientists could finally predict an El Niño months in advance. But a major obstacle remained: They could not reliably predict an event’s strength.
Then came the 1997-98 El Niño. It became the gold standard for super-events, famous for causing catastrophic flooding in California and transforming “El Niño” into a household name.
Forecasters have warned of an impending El Niño for most of a year. Many predictive models have signaled a formidable event, with some hinting at record-breaking territory.
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Where does the name El Niño come from?
Centuries ago, Peruvians noticed that tropical fish would sometimes unexpectedly show up on their shores around Christmas. They called the phenomenon “El Niño,” or “the Christ child” in Spanish. Of course, it took centuries to piece together the bigger picture, and to discover it was Pacific warming that was altering weather patterns around the world.
When will El Niño end?
El Niños rarely last more than a year. The bulge of warm water in the central and eastern Pacific dissipates, usually in the early months of the calendar year after it forms. The trade winds return to normal.
Its effects can linger after it officially ends: The 1991 El Niño led to a below-average hurricane season in the Atlantic, much like this year’s. That El Niño waned at the start of 1992, but still helped delay the start of that year’s hurricane season, which officially began on June 1. The first storm of the season didn’t form until August, but that storm, Hurricane Andrew, quickly intensified into one of the deadliest and most expensive hurricanes in United States history.
There’s also evidence that human-caused climate change is causing strong El Niño conditions to swing more frequently to an opposite phase: La Niña. Among the consequences of La Niña, perhaps the most notable for the United States is stepped-up hurricane activity in the Atlantic Ocean.
What does El Niño do?
The Pacific, the largest ocean, influences atmospheric activity around the world. So when warm water shifts in the Pacific, global patterns of moisture and heat do the same. During an El Niño, some regions might see torrential floods while others are plunged into severe drought. And much of the world gets hotter.
El Niño events also reshuffle global hurricane and cyclone activity, determine which crops flourish or fail and alter the spread of vector-borne diseases. Beneath the surface, the ripple effects are equally profound: Sea levels shift, coral reefs bleach and major fisheries collapse, even as other marine ecosystems enjoy a temporary reprieve.
What happens during a strong El Niño?
Crops can fail. Millions of people can go hungry. Flooding can drive widespread displacement. And recovery can take years. A 2023 study attributed trillions of dollars in global income losses to big El Niño events in 1982-83 and 1997-98.
While the effects differ from region to region, scientists are confident about one global consequence: The world gets hotter.
El Niño events tend to raise the planet’s average temperature during the year in which they form, and the average spikes even higher the year after, as heat from the Pacific continues to dissipate. And this comes on the back of human-caused changes to the atmosphere that are steadily warming the planet.
The three most recent strong El Niño events formed in 1997, 2014 and 2023. Each of those years, at the time, became the hottest on record, only to be later surpassed by 1998, 2016 and 2024. Scientists now widely predict that 2027 will be the hottest year humans have ever experienced.
Will El Niño bring more snow to North America? Less?
The short answer is that it depends.
In the Sierra Nevada and the southern Rockies, snowfall is likely to increase. In these regions, a shifted jet stream frequently delivers above-average precipitation alongside cool winter temperatures, significantly raising the chances for heavy mountain snow.
The northern Rockies face the opposite story. Because storms shift southward during El Niño years, the Pacific Northwest, the northern Rockies and western Canada often end up drier and milder than normal.
Caught in the middle are places like Colorado, where opposing atmospheric signals largely cancel each other out. Facing equal odds of an above- or below-average snow season, the central Rockies are notoriously difficult to make forecasts about. Colorado, like much of the West, had very little snow last winter, devastating many ski resorts and leaving mountains and reservoirs parched.
Across the northern Plains, the Great Lakes and the Northeast, El Niño leans warm. Higher temperatures often reduce total snowfall.
The South also remains a wild card. While a conveyor belt of storms in the South supplies abundant moisture, how or whether that precipitation makes it to the ground hinges entirely on whether brief intrusions of cold air can push far enough south to yield freezing rain, sleet or snow.
Those same systems frequently travel up the East Coast as powerful nor’easters. But because the northern third of the country runs warmer than average during El Niño, these coastal storms often produce rain or treacherous ice rather than just snow.
Still, the sheer frequency of such storms means major snowfalls remain a distinct possibility. It takes only one system to survive the right conditions to drop enough snow to disrupt everyday life for a few days.
What typically happens on the East Coast?
“East Coast locations can see their typical annual flood days jump by 200 to 300% during a strong El Niño event,” said William Sweet, an oceanographer with the National Oceanic and Atmospheric Administration.
Along the Atlantic, the atmosphere is to blame, rather than the ocean. A conveyor belt of winter storms sweeps across the Gulf states and drives winds onto Atlantic shores.
From October to April, coastal towns between New York and Georgia routinely shatter high-tide flood records, not only during severe winter storms, but also on sunny days with no storm in sight.
California gets most of its annual precipitation in the fall and the winter. Even without El Niño, that precipitation often arrives in the form of fierce storms that can drop significant amounts of rain in a short amount of time, leading to flooding or landslides.
El Niño can bring more: more storms, more rain, more flooding, more coastal erosion.
Over and over this summer, giant swells from far-off hurricanes pounded the coast, especially in Southern California, pushing damaging waves into beachfront homes. El Niño helped make this hurricane season an active one in the Pacific and is also contributing to abnormally high sea levels all along the West Coast.
This winter, the day-to-day effects of El Niño will depend on the quantity of storms, their strength and the timing between them.
“If I were betting, I would say we’re going to have above-average rainfall, but a bigger factor is the distribution of that rainfall,” said Jan Null, a veteran meteorologist and a former lead forecaster for the National Weather Service.
If storms are spread out, flooding is minimized and the rainfall and snow are mostly beneficial, feeding rivers and reservoirs. But back-to-back storms can push the rivers over their banks and create life-threatening, costly flooding. A single supercharged system could also stall over land and cause hazardous flooding. The state struggles to capture and store the water for use in dry years.
The season can unfold differently across the state. In the seven strongest El Niños that have occurred since 1950, Southern California received above-normal precipitation during the winter in all of them except one. Northern California also often ends up wetter in an El Niño year, and so far the signal for this year is that this is likely to happen again.
Farther north, into Oregon, Washington and southwestern Canada, El Niño years can often be drier and warmer than usual.
Is this El Niño stronger because of climate change?
There’s El Niño itself, the pattern of shifts in the Pacific and the atmosphere above it. And then there’s El Niño’s effects on weather across the globe.
Those weather effects are occurring against the backdrop of a warming climate that is already juicing up downpours, droughts and wildfires. So when El Niño causes such hazards today, they’re more likely to be more intense than they would have been during a past El Niño of equal strength.
Now, is El Niño itself becoming more intense because of global warming? Hard to say. Some research suggests the answer is yes: As the waters of the Pacific grow warmer and fresher from increased rainfall, it becomes easier for strong El Niños to form. Sea surface temperatures in the area of interest for El Niño formation have been record-breaking.
One recent study used coral skeletons from the Galápagos Islands to reconstruct El Niño activity over the past millennium and found more frequent and stronger events since the 19th century, when industrial activity began heating the planet.
So why is this one stronger?
This El Niño formed just three years after the last major one, which, by El Niño standards, is a very short gap. Is that a coincidence or part of a trend? It could be years before researchers agree on the answer.
For now, what scientists can say is that all the elements that go into an El Niño simply lined up this year. During earlier events, the delicate interplay between the ocean and the atmosphere that produces El Niño conditions hasn’t always been so smooth.
“But this time, the atmosphere is collaborating really, really well,” said Wenju Cai, a climate scientist at the Ocean University of China. “It’s responding to the ocean very, very enthusiastically.”
What can people do to be prepared and limit the damage?
Quite a bit. El Niños are slow-onset events. And people often have months of advanced warning that El Niños are forming, thanks to monitoring buoys in the Pacific.
Some governments have taken steps to build stockpiles of grains and have encouraged farmers to plant drought-resistant seeds. Humanitarian groups have made funding appeals and are positioning food aid in areas they expect will be hard-hit.
Still, El Niños cause many problems in many places, in ways that would strain the aid system even in the best of times. Funding cutbacks from nations like the United States have left holes in the global system for preventing disasters and responding to them. This El Niño could cause nearly 50 million more people across the globe to experience acute hunger, an increase of roughly a fifth, according to the United Nations World Food Program.
This article originally appeared in The New York Times.
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