El Niño is the atmospheric-oceanic phenomenon associated with periodic warming of the eastern tropical Pacific Ocean.
During an El Niño event, sea-surface temperatures become unusually warm across the central and eastern equatorial Pacific. The warming alters the usual trade-wind pattern and shifts rising air, clouds, and heavy rainfall toward different parts of the Pacific basin.
Because the tropical Pacific is tightly connected to the atmosphere, El Niño can influence weather far beyond the ocean. Its effects may include altered rainfall in the Americas, drought in parts of Australia and Indonesia, and changes in global average temperature. The exact consequences vary by event and by season.
El Niño is one phase of the El Niño–Southern Oscillation, or ENSO. Its cooler counterpart is La Niña. The name El Niño means “the little boy” in Spanish and was used by Peruvian fishers in reference to the Christ Child because the warm current often appeared around Christmas.