El Niño is a weather phenomenon characterized by abnormally high surface temperatures in the tropical Pacific Ocean, and weaker trade winds, which have been known to cause a global ripple effect of turbulent and unusual weather. The effect is caused in large part by the weakening of trade winds, which normally push the warmer surface water of the Pacific westward. As these winds grow weaker, they allow warm surface water to change course and ebb eastward. As sea and sky encourage different behavior in one another, jet streams change course, causing storm systems to show up in locations they normally don't. This weather condition can often cause fishing populations to die off, as they are unable to cope with drastic changes in sea temperature. It also tends to make hurricane season around Central and North America less fierce.
Scientists aren't exactly sure what causes El Niño conditions, but they are quite good at anticipating them. Buoys placed throughout the Pacific Ocean detect water levels and temperatures, letting researchers know of any abnormal conditions. Although the weather ramifications from one El Niño to the next aren't exactly the same, researchers forewarned by data about an upcoming El Niño season are able to give the public a general idea of what to expect. More research is being conducted in the attempt to understand exactly what causes periodic and drastic changes in the Pacific Ocean's climate.
El Niño conditions in the Pacific are something of a climate flip-flop. In normal conditions, eastern countries in the South Pacific, such as Australia and Indonesia, experience heavy rainfall. During seasons with strange weather patterns, however, these countries often experience drought-like conditions. Conversely, western countries around the South Pacific experience abnormally high precipitation. Peru, for instance, experiences heavy rainfall and flooding. Temperatures in the United States plummet far below standard temperatures in certain areas of the country, causing severe winter weather systems, while other states experience less precipitation. This topsy-turvy reversal is known as the El Niño southern oscillation (ENSO), as it resembles a kind of see-saw of weather patterns.
El Niño is Spanish, and literally means "the boy," but it's better understood in its colloquial use in South America, where it often refers to the baby Jesus. South American fisherman came up with this name because the strange weather patterns they witnessed tend to occur around Christmas. It was also fitting that researchers gave weather patterns opposite to El Niño the name La Niña.