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What is El Niño?

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Have you ever heard a news headline mentioning that unusual  or extreme weather is expected due to El  

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Niño? It’s something that we hear about  every few years or so in North America.

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But what exactly is El Niño? And what  does it have to do with our weather? 

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El Niño is a powerful weather pattern  that occurs in the Pacific Ocean,  

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but it can affect weather around the world.

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Under normal conditions, strong  winds along the equator push warm  

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water at the surface of the ocean from  South America west toward Indonesia.

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But, in an El Niño year, things are different.  In fall and winter of an El Niño year, the winds  

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at the equator grow much weaker than usual. This causes warm water to shift back toward  

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the coast of South America. When that  happens, it can really shake things up! 

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That’s because El Niño doesn’t just stay in the  ocean—it changes the weather, too. Because of El  

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Niño, some places in the United States and Central  and South America get way more rain than usual. 

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Very heavy rains and storms can sometimes  lead to flooding in these regions. 

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At the same time, other places can get less  rain than usual and experience droughts.

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Wildlife can be affected by El Niño, too.  For example, fish that usually live in  

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cooler waters might swim away to new areas  because of the warmer ocean temperatures. 

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So, how do scientists know when El Niño is  happening? They use satellites to keep an  

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eye on the ocean's temperature from space! Weather satellites, such as those in NOAA’s  

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GOES-R series, can use instruments to collect  information about sea surface temperature. 

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Meteorologists can use this information to  help predict if an El Niño pattern is forming.  

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This advanced notice can help to help people  in affected areas prepare for its effects.

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Find out more about Earth’s  weather at NOAA SciJinks!