Several international weather bureaus have detected the development of El Niño conditions in the eastern Pacific Ocean and predicted that these conditions will continue to strengthen throughout the remainder of 2015, peaking sometime between October and December.

El Niño episodes happen every few years when unusually warm ocean conditions occur along the tropical west coast of South America. They are associated with adverse effects on fishing, agriculture, and local weather from Ecuador to Chile. They are also associated with reduced precipitation in the equatorial western Pacific Ocean and Australia, increased rainfall in California, quieter Atlantic hurricane seasons, and milder winters in eastern North America.

During the 20th century the El Niño episodes of 1982–83 and 1997–98 were most intense. In the 1982–83 episode, Australia was hit by drought and flooding, and the west coast of North America was unusually stormy during the winter of 1982–83; fish catches were dramatically altered from Mexico to Alaska. The El Niño episode of 1997–98 is regarded by some scientists as the strongest of the 20th century. It brought drought to Brazil, Indonesia, Malaysia, and the Philippines, drenched Peru’s dry seacoast with heavy rain, and delivered record-breaking warm temperatures to the Upper Midwest in the U.S., causing some journalists to label the period “the year without a winter.”

Some climate models predict that the 2015–16 El Niño will be stronger still.