El Niño is the climate phenomenon involving unusually warm sea-surface temperatures in the central and eastern tropical Pacific Ocean. It is the warm oceanic phase of the broader El Niño–Southern Oscillation, or ENSO, which links ocean temperatures with shifts in atmospheric pressure and winds.
During a typical El Niño, weakened trade winds allow warm surface water to move eastward toward South America. This reduces the usual upwelling of cold, nutrient-rich deep water along the Peruvian and Ecuadorian coasts. The resulting rearrangement of tropical heat can alter rainfall, drought risk, storms, and temperatures far beyond the Pacific.
The name comes from “El Niño,” Spanish for “the boy,” referring historically to the Christ Child because the warming was often noticed around Christmas by coastal fishers in Peru. La Niña is the contrasting cool phase, while ENSO-neutral conditions lack a strong warm or cool anomaly.
El Niño is not simply a warm ocean current or a local Pacific event. Its atmospheric teleconnections can influence weather patterns across the Americas, Asia, Australia, and parts of Africa, although the exact effects vary by event and season.