
El Nino is a temporary change in the climate of the Pacific ocean, in the region around the equator, the wind blows strongly from east to west along the equator in the Pacific. This actually piles up water about half a meter in the western part of the Pacific. In the eastern part, deeper water which is colder than the sun-warmed surface water gets pulled up from below to replace the water pushed west. So, the normal situation is warm water which is about 30 C in the west, cold about 22 C in the east. In El Nino, the winds pushing that water around get weaker. As a result, some of the warm water piled up in the west slumps back down to the east, and not as much cold water gets pulled up from below. Both these tend to make the water in the eastern Pacific warmer. But it doesn't stop there. The warmer ocean then affects the wind and it makes the winds weaker and is what makes an El NiƱo grow. A strong El Nino is often associated with wet winters over the southeastern US, as well as drought in Indonesia and Australia
