El Nino climate pattern, illustration. El Nino is a naturally occurring climate pattern that describes the warming of surface waters in the eastern Pacific Ocean. It is the warm phase of a larger phenomenon called the El Nino-Southern Oscillation (ENSO) that occurs roughly every 5 years. El Nino affects weather and storm patterns in different parts of the world. The onset of this phenomenon is expected to trigger more extreme heat in many regions, leading to more temperature records being broken.