El Niño and its opposite, La Niña
El Niño forms when surface temperatures in the tropical Pacific Ocean are about 0.5°C (0.9°F) above normal for three months. La Niña is the reverse, with temperatures cooler than normal. The chart shows the three-month rolling average temperature anomaly.
A line chart shows 73 years of El Nino and La Nina periods, which seesaw back and forth every few years.
