El Niño and its opposite, La Niña, since 1950
El Niño forms when surface temperatures in the tropical Pacific Ocean are about 0.5°C (0.9°F) warmer than normal for three months. A strong El Niño has temperatures over 1.5°C (2.5°F) above the long-term average. The chart shows the Relative Oceanic Niño Index, a three-month rolling average that removes the background influence of global warming for comparison.
A line chart shows 75 years of El Nino and La Nina periods, which seesaw back and forth every few years.
