How El Niño Could Shape US Winter Weather

A patch of ocean thousands of miles from the US is likely to have a major say in this winter’s weather. Experts now give better than an 83% chance that the current El Niño will be strong to very strong through early 2027. They say it could become the strongest since record-keeping began in 1950.   

El Niño is a natural climate pattern. It's in effect when surface waters in the Pacific become warmer than normal. It recurs about every 2 to 7 years. The warmer water changes how air moves above the ocean. That effect shifts rainfall and temperature patterns worldwide.    

In the US, El Niño’s biggest effect is on the jet stream. It's a fast-moving current of air high in the atmosphere that steers storms. The National Oceanographic and Atmospheric Administration (NOAA) predicts El Niño will nudge the jet stream south and east from December through February. The likely result is a wetter-than-average winter across the southern US and along the East Coast. And it likely means a warmer-than-average one across much of the northern US. That includes the Pacific Northwest and Midwest. 

Increased rainfall could ease drought across much of the country. But it carries risks, too. Ken Graham warned in a press release that heavy rain on dry soil can lead to flash flooding and mudslides. Graham is the head of NOAA’s National Weather Service.   

Experts warn the outlook is not a guarantee. It just provides the odds something might happen. It doesn’t predict snowfall totals. Snow can’t be reliably forecast more than about a week ahead. And recent history suggests some caution. The very strong El Niño of 2015-16 was expected to drench Southern California. Instead, the region ended that winter with below-average rainfall. Unusually warm water in the western Pacific and Indian oceans helped steer storms farther north that year.

El Niño, in other words, makes some things more likely. But whether they happen depends on the rest of the atmosphere.  

Reflect: When someone says something is “likely” to happen, how much do you count on it?