|An El Niņo occurs when the atmosphere and ocean waters interact to form warmer than normal water in the eastern and central Pacific Ocean. Sometimes an El Niņo is followed by a La Niņa whose effects on weather patterns are generally opposite to those caused by an El Niņo.
(Top) Normal sea surface temperatures. (Middle) Sea surface temperatures during an El Niņo. Notice the red areas to the west of South America. (Bottom) Sea surface temperatures during a La Niņa. Notice the blue areas to the west of South America.