What is "El Niño" and what are its effects?

The term El Niño (Spanish for 'the Christ Child') refers to a warming of the ocean surface (or above-average sea surface temperatures) in the central and eastern tropical Pacific Ocean. The low-level surface winds, which normally blow from east to west along the equator (“easterly winds”), instead weaken or, in some cases, start blowing the other direction (from west to east or “westerly winds”). El Niño recurs irregularly, from two years to a decade, and no two events are exactly alike. El Niño events can disrupt normal weather patterns in the United States and globally.

Although the USGS doesn’t directly study or forecast the weather (our sister agency, NOAA, and its National Weather Service do), the USGS studies and documents the effects and impacts of long-term climate changes and weather phenomena across the U.S. and globally.