How often does El Niño happen and why?

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El Niños occur irregularly approximately every two to seven years. Warm water generally appears off the coast of South America close to Christmas, and reaches its peak warmth in the eastern Pacific during the late fall of the following year. read more

•Climate records of El Niño go back millions of years, with evidence of the cycle found in ice cores, deep sea muds, coral, caves and tree rings. •Record rainfall often strikes Peru, Chile and Ecuador during an El Niño year. read more

El Niño results from interaction between the surface layers of the ocean and the overlying atmosphere in the tropical Pacific. It is the internal dynamics of the coupled ocean-atmosphere system that determine the onset and termination of El Niño events. read more