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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), a recurring pattern in which the tropical Pacific Ocean and atmosphere change together. It shifts tropical rainfall and atmospheric circulation, which can alter seasonal odds of rain, drought, and storm activity far from the Pacific. It does not determine the weather in any one place or guarantee a particular storm or season.
What El Niño is
During El Niño, sea-surface temperatures become unusually warm in the central and eastern equatorial Pacific. The easterly trade winds weaken, allowing warm surface water to shift east. Tropical clouds and rainfall tend to follow the warmer water, changing where heat and moisture enter the atmosphere.
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The resulting atmospheric response can alter pressure patterns, jet streams, and storm tracks well beyond the tropics. NOAA emphasizes that El Niño requires a coupled ocean-and-atmosphere response: warm water by itself is not enough to define the phenomenon. NOAA: What are El Niño and La Niña? and NOAA: ENSO
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El Niño occurs irregularly, on average every two to seven years, and typically lasts nine to twelve months, according to NOAA. Events differ in strength, timing, and development, so their effects are not identical. NOAA: What are El Niño and La Niña?
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How the Pacific pattern affects weather elsewhere
As the main zone of tropical rain shifts east, it changes the circulation of the atmosphere. Those changes can influence large-scale pressure patterns and the paths followed by storms. The resulting connections between a tropical climate pattern and weather in a distant region are often called teleconnections.
These connections describe shifts in probability, not a local forecast. A seasonal outlook also depends on the time of year, the event’s evolution, and other climate influences. Historical El Niño patterns can indicate which conditions are more likely; they cannot say exactly how much rain a particular town will get or whether it will experience a specific storm.
Common regional effects
Equatorial Pacific and nearby tropics
Rainfall tends to increase over the central and eastern equatorial Pacific, while areas around the wetter zone often become drier. Indonesia, the western equatorial Pacific, and northern Australia commonly experience suppressed rainfall and higher pressure. NOAA: ENSO and global warming—what’s the difference?
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El Niño can bring unusually heavy rain to parts of Peru, Ecuador, and Chile. The risk and location of impacts vary; the pattern does not mean every place in these countries will be unusually wet during every event. NOAA: ENSO and global warming—what’s the difference?
Australia, Indonesia, and parts of southern Asia
With tropical rainfall concentrated farther east, drought risk can rise in Australia, Indonesia, and parts of southern Asia. This is a broad tendency rather than a guarantee that a given country or location will have a drought. NOAA: ENSO and global warming—what’s the difference?
The United States in winter
In Northern Hemisphere winter, a stronger or farther-east Pacific jet stream often helps steer storms along a different path. NOAA describes wetter and cooler-than-normal conditions as typical across the southern tier, from central California toward Florida and up the East Coast. The northern United States toward the Great Lakes tends toward warmer and drier-than-average conditions. These are seasonal patterns, not a prediction for every state or winter; other climate patterns also influence outcomes. NOAA Climate Prediction Center: ENSO FAQ
Tropical cyclones
El Niño tends to hinder hurricane formation in the Atlantic basin while favoring tropical cyclone activity in the central and eastern Pacific. This describes a seasonal influence on basin-wide activity, not whether a particular storm will form or where it will travel. National Hurricane Center: Tropical cyclone climatology
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Marine life and fisheries
Warmer water and altered currents can change the distribution and abundance of fish and other marine species off northern South America. Strong events can affect marine life farther north as well. NOAA: What are El Niño and La Niña?
El Niño, La Niña, and neutral conditions
ENSO has three phases: El Niño, La Niña, and neutral. El Niño is associated with unusually warm surface water in the central and eastern equatorial Pacific; La Niña generally involves cooler-than-usual water there, while neutral conditions fall between the two. The phases also differ in their wind and tropical-rainfall patterns.
El Niño and La Niña often produce contrasting effects in the tropical Pacific, but their impacts in distant regions are not perfect opposites. A useful comparison must account for the location of the Pacific temperature anomaly, the ocean-atmosphere response, the season, the region, and the uncertainty in a forecast. NOAA: ENSO
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How NOAA monitors El Niño
NOAA’s Climate Prediction Center (CPC) changed its operational index for monitoring ENSO on February 1, 2026, adopting the Relative Oceanic Niño Index (RONI). RONI helps describe Pacific temperature anomalies relative to the tropical oceans more broadly. CPC’s strength outlook synthesizes observations and multiple models, with ranges and uncertainty; an index value alone does not tell you how severe local impacts will be. NOAA CPC: ENSO Diagnostic Discussions
Earlier CPC guidance described a traditional El Niño temperature criterion as a three-month average sea-surface temperature departure above +0.5°C in the east-central equatorial Pacific, alongside an atmospheric response. That historical threshold should not be treated as the whole of NOAA’s current operational monitoring after its transition to RONI. NOAA Climate Prediction Center: ENSO FAQ and NOAA CPC: ENSO Diagnostic Discussions
NOAA’s September 10, 2026 outlook
In its September 10, 2026 ENSO Diagnostic Discussion, NOAA CPC reported that El Niño was strengthening. The outlook gave a greater than 90% chance of a very strong event during Northern Hemisphere fall and winter 2026–27, and a 75% chance in October–December 2026 of a historic event, defined in that outlook as a three-month RONI value of +2.5°C or higher. These are forecast probabilities, not observed outcomes. NOAA CPC: ENSO Diagnostic Discussions
NOAA cautioned, “With an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, though not guaranteed.” A very strong ENSO signal can raise the odds of characteristic patterns without making impacts equally strong everywhere or determining any particular region’s weather. The forecast is dated September 10, 2026; CPC’s discussion named October 8, 2026 as its next scheduled update, so the probabilities should not be read as a current outlook after a newer discussion is issued. NOAA CPC: ENSO Diagnostic Discussions
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