El Niño means The Little Boy, or Christ Child in Spanish. El Niño was originally recognized by fishermen off the coast of South America in the 1600s, with the appearance of unusually warm water in the Pacific Ocean. The name was chosen based on the time of year (around December) during which these warm waters events tended to occur.
The term El Niño refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific.
El Niño is the warm recurring climate pattern across the tropical Pacific. The pattern can shift back and forth irregularly every two to seven years, and trigger predictable disruptions of temperature, precipitation, and winds.
These changes disrupt the large-scale air movements in the tropics, creating global side effects. El Niño is anchored in the tropical Pacific, but it affects seasonal climate "downstream" in the United States, but not all impacts occur during every event, and their strength and exact location can vary. For the United States, the most significant impact is a shift in the path of the mid-latitude jet streams. These swift, high-level winds play a major role in separating warm and cool air masses and steering storms from the Pacific across the U.S. Typical El Niño effects are likely to develop over North America during the winter season. Those include warmer-than-average temperatures over western and central Canada, and over the western and northern United States. Wetter-than-average conditions are likely over portions of the U.S. Gulf Coast and Florida, while drier-than-average conditions can be expected in the Ohio Valley and the Pacific Northwest. The presence of El Niño can significantly influence weather patterns, ocean conditions, and marine fisheries across large portions of the globe for an extended period of time.