There is a 50% to 60% chance that El Niño will develop during the July to September window and beyond, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). The World Meteorological Organization recently updated its outlook. Here is what to know about El Niño and its cooler sister, La Niña.
Where the name comes from
El Niño and La Niña are two phases of a natural climate pattern in the tropical Pacific known as the El Niño-Southern Oscillation (ENSO). Peruvian and Ecuadorian fishermen coined the term El Niño in the 19th century for the arrival of an unusually warm ocean current off the coast that thinned their catch shortly before Christmas. Scientists chose La Niña as its opposite. Between the two lies a neutral phase.
How El Niño works
El Niño can weaken the trade winds that blow from east to west across the tropical Pacific, shifting the movement of warm water across that vast ocean. That weakening warms the normally cooler central and eastern Pacific and rearranges rainfall and wind patterns worldwide. The extra surface heat releases energy into the atmosphere and can temporarily raise global temperatures, which is why El Niño years often rank among the warmest on record.
According to Nat Johnson, a NOAA meteorologist, a typical El Niño event tends to cause a temporary rise in the global average temperature of about 0.1°C to 0.2°C (0.2°F to 0.4°F). The phenomenon occurs every two to seven years. It usually brings drier conditions to Southeast Asia, Australia, southern Africa and northern Brazil, and wetter ones to the Horn of Africa, the southern United States, Peru and Ecuador.
Another record?
The last El Niño ran from 2023 to 2024. Now there is growing concern that 2026 could be the hottest year ever recorded, even without El Niño, because of the underlying warming trend. Carlo Buontempo, director of the European Union’s Copernicus Climate Change Service, said 2026 could be another record year if El Niño develops.
The impact, however, would be greater in 2027 than in 2026 if the phenomenon appears in the second half of the year, said Tido Semmler, a climate scientist at Ireland’s national weather service. The global atmosphere takes time to react to El Niño. Even so, he warned, the risk of a record 2026 exists regardless.
La Niña, the other face
The latest La Niña was relatively weak and short-lived, running from December 2024 into a neutral phase in early 2025. La Niña cools the eastern Pacific for one to three years and produces the opposite effects: wetter conditions in parts of Australia, Southeast Asia, India, southeastern Africa and northern Brazil, and drier ones in parts of South America. Even so, it did not stop 2025 from being the third-hottest year on record.
A new way to measure it
In February, NOAA adopted a new method for defining these events. The old Oceanic Niño Index (ONI) compared sea-surface temperatures in a Pacific region against a 30-year average. But as the oceans warm quickly, that average has become outdated. The new Relative Oceanic Niño Index (RONI) compares how warm or cool the central-eastern Pacific is relative to the rest of the tropics, which NOAA calls a clearer, more reliable way to monitor El Niño and La Niña in real time.
For the Amazon, the stakes are not abstract: a strong El Niño usually means drought in northern Brazil, with a higher risk of fires and lower river levels. That is why every NOAA and WMO forecast is watched closely across the region.
Reporting: Anne Silva / Amazonia Mag. Sources: NOAA; World Meteorological Organization; Copernicus (EU); AFP.