A disruption of the oceanic-atmospheric system in the tropical Pacific that strongly affects weather conditions across the globe for a few months to up to one year with a seemingly random frequency. El Niño is watched in the agricultural commodities markets because the phenomenon can have substantial effects on crops in affected areas. El Niño increases rainfall across the southern part of the United States and in Peru. Drought conditions can be produced in the West Pacific, which leads to brush fires in Australia and Indonesia. Its most severe effects occur close to the equator. Warmer water near Central America spawns more frequent and stronger hurricanes, which can occur as far west as Hawaii. El Niño occurs in contrast to La Niña, which produces cold events.

El Niño was first recognized by fishermen off the coast of South America when unusually warm water in the Pacific Ocean arrived near the beginning of the year. The term El Niño means “the little boy” or “Christ child” in Spanish. The name was given because the warm water arrived around Christmas.