El Niño is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean. It is the warm phase of the El Niño-Southern Oscillation (ENSO) cycle, which is a cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean. During El Niño, a band of warm ocean water develops in the central and east-central equatorial Pacific, including the area off the Pacific coast of South America. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific.
El Niño and La Niña are two opposing climate patterns that break the normal conditions of the Pacific ocean. During normal conditions, trade winds blow west along the equator, taking warm water from South America towards Asia. To replace that warm water, cold water rises from the depths, a process called upwelling. El Niño and La Niña can both have global impacts on weather, wildfires, ecosystems, and economies. Episodes of El Niño and La Niña typically last nine to 12 months, but can sometimes last for years. El Niño and La Niña events occur every two to seven years, on average, but they don’t occur on a regular schedule.
