This summer was already predicted to be hot for much of the planet, after a near-record year of global heat last year. But El Niño – the influential weather pattern associated with heat, unlike the cooler La Niña – has arrived and it's raising more alarm.
"If we have a big El Niño on top of the long-term warming trend, that just really enhances the probability that we'll see a new record global mean temperature," says meteorologist Nat Johnson of the National Oceanic and Atmospheric Administration, who is part of the El Niño forecasting team.
Officials from Europe to India and Australia are warning of potential harmful effects, including heat waves and abnormally dry conditions.
"Even though it's a phenomenon that's rooted in the tropical Pacific," Johnson says, global jet streams transfer El Niño's influence far and wide.
"Basically, every continent, you'll see some sort of impact from an El Niño or a La Niña event," he says. Some of that impact, he says, is economic, from disrupted marine ecosystems and fisheries.
El Niño effects start in the tropics, and then spread
"The strongest impacts initially will tend to be in the tropical regions," Johnson says, adding that El Niño tends to bring enhanced drought to a wide band of locations, from Indonesia to the northern Amazon.
And this year's El Niño is shaping up to be a strong one.
"There is a 63% chance of a very strong El Niño [from November to January] that would rank among the largest El Niño events in the historical record going back to 1950," NOAA said in an advisory.
"This could be a very significant event in 2026 and lingering into 2027," says Daniel Swain, a climate scientist with University of California Agriculture and Natural Resources.
A strong El Niño would drive up average global temperatures. The hottest years on record generally occur in years when El Niño is active, because it occurs when the Eastern Pacific is hotter than usual.
The U.S. could see a variety of impacts
How a strong El Niño will affect the U.S. is more difficult to predict.
"What we experience in our own backyard is usually going to be a combination of many different things, including potentially El Niño," Johnson says.
It comes down to where the ocean's heat is released – and how that affects air circulation, temperatures, and precipitation thousands of miles away.
During a typical El Niño, Johnson says, "impacts tend to be strongest in the mid-latitudes and the higher latitudes in the late fall and winter seasons."
The southern U.S. mainland would see wetter weather, while the northernmost contiguous U.S. would see warmer conditions, Johnson says, adding that the Pacific Northwest tends to be drier.
On the eastern side of the U.S., El Niño makes it harder for hurricanes to form in the Atlantic Ocean, so they often coincide with less severe hurricane seasons. However, El Niño offers limited protection, since it only takes one major storm making landfall to cause catastrophic damage. Climate change has also caused temperatures in the Atlantic to soar, providing more fuel for storms that do form. And El Niño does nothing to temper storms that form in the Pacific.
How an El Niño forms
El Niño occurs when trade winds weaken, allowing vast volumes of warm ocean water to move from the Eastern Pacific toward the Americas.
"Its function in the global earth system is to release heat from the deeper oceans that has been temporarily stored there," Swain says. "El Niño allows that subducted heat to be unearthed."
That dynamic played out in a big way in 2023 and 2024, when a long, strong El Niño pattern helped shatter global temperature records. 2023 smashed the record for the hottest year ever recorded on Earth, only to be surpassed by temperatures in 2024.
El Niño, which is a natural cyclic fluctuation, is just one driver of such record-breaking heat. Human-caused global warming from burning fossil fuels is the main reason that the planet is warming. Even without El Niño, last year was in the top three hottest years on record.
NPR's Rebecca Hersher contributed to this story.
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