El Niño (also known as ENSO or the El Niño Southern Oscillation), is a large patch of warm water that moves between the eastern and western Pacific Ocean near the equator. When the warm water (about one degree Celsius warmer than normal) of El Niño is near South America, the warm water affects the weather in the southwestern United States by increasing rainfall, and is responsible for changes in the weather throughout the world. El Niño lasts for about four years in the eastern Pacific Ocean and then returns to the western Pacific near Indonesia for another four years. When the warm water is in the western Pacific, it is known as La Niña, the opposite of El Niño. When La Niña is in action, we have “normal” climatic conditions.