La Niña is a climate pattern characterized by the cooling of sea surface temperatures in the central and eastern tropical Pacific Ocean, which often leads to significant weather changes globally, including increased rainfall in Southeast Asia and droughts in the western Pacific and South America. It typically occurs every two to seven years, lasting nine to twelve months, and is part of the larger El Niño-Southern Oscillation (ENSO) cycle, which has profound impacts on global climate and weather patterns.