The climate pattern associated with unusually warm tropical Pacific Ocean waters is El Niño. It is the warm phase of the El Niño–Southern Oscillation, or ENSO, a coupled pattern involving the tropical Pacific Ocean and atmosphere.
During El Niño, sea-surface temperatures become warmer than average in the central and eastern equatorial Pacific. The warming can weaken or shift the normal tropical circulation, affecting rainfall, winds, and storm patterns far beyond the Pacific region.
Its effects vary by location and event. Some regions experience increased rain and flooding, while others become unusually dry. El Niño is not simply a worldwide warming event and does not produce identical weather every time. Its cooler counterpart is La Niña, while the neutral phase lacks the major warm or cool Pacific anomaly.