El Niño is a naturally occurring phenomenon of periodic warming of sea surface temperatures in the central and eastern regions of the Pacific Ocean. La Niña is the opposite, describing cooler-than-average sea temperatures. Both El Niño and La Niña significantly affect Earth's weather patterns.
El Niño and La Niña events occur every two to seven years on average and usually last between nine to 12 months, but can sometimes persist for years. According to the National Oceanic and Atmospheric Administration (NOAA), El Niño generally occurs more frequently than La Niña.
