In the 19th century, South American fishermen noticed unusually warm waters around Christmas. They dubbed the phenomenon “El Niño” which directly translates to “the little boy,” according to National Geographic.
Today, scientists have a greater understanding of how those temperature shifts in the equatorial Pacific Ocean impact global weather patterns, especially across the Americas. And even the most casual of weather watchers know the phrase well.
But what does it mean?
El Niño occurs when rising surface temperatures combine with specific atmospheric conditions and rainfall patterns, according to National Geographic.
As a 2026 forecast is predicting an El Niño, many are asking: What is the difference between El Niño and its counterpart, La Niña and could the world face a Super El Niño?
What are La Niña and El Niño
During La Niña, trade winds that blow from east to west strengthen. This allows “upwelling” — when cold water rises from lower levels in the ocean — to occur along the Americas, according to Fox Weather.
On the other hand, El Niño develops when those trade winds weaken. Warm water moves east, causing moisture to rise into the atmosphere and disrupting weather across the Americas, according to the National Oceanic and Atmospheric Administration report.
The NOAA report characterizes an official El Niño by:
- Equatorial Pacific surface temperatures rising 0.5 degrees Celsius (0.9 degrees Fahrenheit) above average.
- The trend lasting for three consecutive months.
- Changes in atmospheric pressure and rainfall.
The impacts from both La Niña and El Niño on climate and weather can last nine to 12 months sometimes even years, NOAA’s National Ocean Service.
The Super El Niño and what to expect in 2026
Meteorologists typically use the term Super El Niño when temperatures climb 2 degrees Celsius above normal. Meteorologists will compare specific Pacific temperatures to the average temperatures in the area and compared to the rest of the tropical oceans to determine that 2 degree threshold. If the entire ocean sees a rise in temperature, the specific effects of the phenomenon may be less obvious as there won’t be such a drastic contrast in temperature, according to Fox Weather.
What to expect in 2026
The April NOAA report also issued a La Niña advisory and an El Niño watch. The climate is currently transitioning to ENSO neutral conditions, where the atmosphere and ocean aren’t quite aligned enough to trigger either phenomenon, according to the National Weather Service.
This neutral phase is expected to last through July.
Right now, NOAA estimates that El Niño has a 62% chance of emerging between June and August and will last until the end of 2026.
“In the just-released April ENSO outlook from the European Centre for Medium-Range Weather Forecasts, every one of the 20-plus model ensemble members is predicting moderate or strong El Niño conditions by mid-June,” wrote Bob Henson and Jeff Masters in Yale Climate Connections, according to Forbes.
By October, those models suggest that temperatures will exceed the 2 degree Celsius threshold.
If El Niño strikes, the U.S. will likely see:
- Above-average heat in the West, South, Northeast and Alaska.
- Increased rainfall in the Southeast and Mid-Atlantic, while the Pacific Northwest and Northern Rockies may face drier conditions.
- Reduced hurricane activity in the Atlantic, but the 2026 impact remains uncertain.
Global impacts
The phenomenon does more than change the daily forecast.
When the warm ocean water pushes the cold to the bottom of the ocean, it blocks nutrient dense water from upwelling from the bottom and reaching the surface, disrupting marine ecosystems, according to National Geographic.
On land, in southeast Asia and Australia, droughts, wildfires and colder ocean waters impact the environment. In 1997 through 1998, El Niño caused $33 billion in damages and thousands of deaths. It brought record flooding to Peru, flash floods in Mississippi and California and tornadoes to Florida, according to National Geographic.