June 1 marks the beginning of hurricane season, but recent news headlines have been dominated by another ocean-related phenomenon: El Niño. And many experts are saying this El Niño is shaping up to be a strong or “super” one.
It sounds ominous, especially after a winter where residents of New York City saw one of the coldest and snowiest seasons in a decade. Yet elsewhere, including parts of Texas and the Plains, residents saw record warmth and severe drought during this same period. If such stark contrasts can occur during a time when scientists are forecasting relatively weak El Niño conditions, what could be coming if a true “super” El Niño develops?
What is El Niño?
In short, El Niño is “a change in the surface water temperatures in the tropical Pacific,” says Muhammad Azhar Ehsan, an associate research scientist at the Columbia Climate School. If the water is warmer than usual, that can trigger an El Niño effect. Colder than usual often leads to La Niña.
What causes these shifts in ocean water temperature? They are part of a naturally occurring climate pattern called the El Niño-Southern Oscillation, or ENSO for short. Normally, trade winds blow west along the Earth’s equator, pushing warm water from South America toward Asia. But sometimes the trade winds weaken and warm water “sloshes” back toward South America. This results in warmer-than-average ocean temperatures in the central and eastern tropical Pacific Ocean, and significant changes in global weather patterns—among them milder winters in the northern United States and wetter conditions in the southern parts of the country.
The phrase El Niño “comes from Spanish meaning ‘Christian boy,’” says Mingfang Ting, a professor of climate at the Columbia Climate School. “This phenomenon usually happens around Christmas time,” when El Niño often peaks.
Frequently, a La Niña climate pattern will emerge after an El Niño one. This happens when the east-to-west trade winds strengthen and push warm surface water farther west, toward Indonesia and Australia. When this happens, cold water rushes up from the deep ocean near South America to replace the warm water. These shifts can alter weather patterns not just in these areas, but all over the world. During La Niña, for example, winters in the northern U.S tend to be cooler and wetter, while the southern part of the country experiences warmer, drier conditions.
When sea surface temperatures in the Pacific are neither abnormally warm nor cold, the climate system is said to be in an ENSO neutral phase. The cycle of El Niño, La Niña, and ENSO neutral does not occur on a regular schedule, but it typically happens every two to seven years and each phase lasts an average of nine to twelve months.
From December 2025 through February 2026, the Pacific experienced a weak La Niña phase that began to transition into ENSO neutral conditions. There is an 82 percent chance that El Niño will emerge this summer and last through the end of 2026, according to the National Oceanic and Atmospheric Administration (NOAA).
Scientists are confident El Niño will emerge. “The tropical Pacific is already showing several classic early warning signs,” says Ehsan. “Subsurface ocean temperatures across the central and eastern equatorial Pacific have become significantly warmer than average, and that excess heat is beginning to rise toward the surface—a key ingredient for El Niño formation.”
But what’s capturing everyone’s attention is NOAA’s prediction that there is, as of press time, a 37 percent chance that a “very strong” El Niño event could develop later this year.
What will a very strong El Niño mean for the U.S.?
A “very strong” El Niño means the surface waters of the Pacific Ocean around the equator are more than 2 degrees Celsius warmer than average. When scientists study ENSO, they look at how much the Pacific sea-surface temperatures deviate from long-term averages to classify a system’s intensity:
- Weak: 0.5 to 0.9 °C warmer than normal
- Moderate: 1.0 to 1.4 °C warmer than normal
- Strong: 1.5 °C to 2.0 °C greater than normal
- Very Strong: Anomalies exceeding 2.0 °C
Since 1980, there have only been three El Niño events classified as “very strong” or “super.”
The 1982-1983 El Niño was called “the strongest and most devastating of the century” because the trade winds collapsed and reversed, causing weather disasters on nearly every continent. Australia, Africa and Indonesia experienced droughts, dust storms and wildfires, while Peru and portions of South America saw some of the heaviest rainfall in recorded history. That El Niño event was blamed for nearly 2,000 deaths and more than $13 billion in damages.
In December 1997, a very strong El Niño brought wetter-than-normal conditions across most of the southern U.S., while the northern states experienced warmer-than-average temperatures, making it the second warmest and seventh wettest winter since 1895. In January and February of 1998, the national average was nearly 2.8 degrees C warmer than normal and the country received an average of 6.01 inches of rain compared to the normal of 4.05 inches.
2015 was the last very strong El Niño event, when the tropical Pacific Ocean averaged 2.4 degrees C higher than normal. That year, the Northern Pacific saw a record 16 tropical cyclones; a 500-year drought in the Caribbean led to water rationing in Puerto Rico; and global surface temperatures were so hot that 2015 took the dubious honor of being the warmest year on record. Still affected by El Niño, 2016 was even hotter, holding the all-time record until 2023.
One might assume that a warming planet would super-charge ENSO, leading to more intense cycles, but scientists aren’t entirely certain how much climate change influences El Niño. “Even though we have a huge increase of global mean surface temperature, El Niños are not becoming stronger,” says Ting.
Given how rare “very strong” El Niño events have been, scientists say their occurrence alone is not necessarily an indication of more intense weather impacts. “El Niños are very unique in their development,” says Ehsan. “Their impacts depend on the strength, timing and interaction with other climate patterns in the atmosphere and oceans.”
Ehsan is a member of the CPC/NOAA advisory group that develops the monthly ENSO forecast. The CPC predicts above-average temperatures for most of the U.S., while portions of the East Coast and southwest U.S. will see above-average precipitation, according to its June-August 2026 seasonal outlook. With an 82 percent chance that El Niño will emerge during the May-July period, Ehsan anticipates more active, wetter storms in the south, warmer-than-normal temperatures in the north, and a heightened potential for costly weather events.
All of this sounds quite ominous, but it’s not all doom and gloom, says Andrew Kruczkiewicz, a meteorologist and a senior staff associate with the Columbia Climate School. “A lot has changed in the early warning system and preparedness context over the past 30 years,” Kruczkiewicz says, referring to the record-breaking El Niño of 1997-1998. “We have more tools, more data, better forecasting and ways to monitor the evolution of El Niño and its potential impacts.”
There’s also an upside to having a “super” El Niño (or La Niña), as when the strength of El Niño or La Niña increases, so does the predictability in the climate system, says Kruczkiewicz, “and we have more confidence in our forecasts.”
More predictability means more of an opportunity to act, he adds, and justifies the spending of funds on preparedness. “If done at a sufficient scale,” he says, “emergency managers, energy companies, public health officials and the like will have more time and resources to take anticipatory and risk-reducing actions.”
As of press time, Ehsan had this to add: “The latest observations, including various traditional El Niño indices, continue to nudge the outlook a bit closer toward a stronger event. But, as we’ve often noted, every ENSO event is unique, and so are its impacts. The strength of the event is only part of the story.”
Ehsan says he and his team have something new coming later this month: El Niño strength-probability estimates. Check back here for an update on June 19.
