La Niña is associated with cooler than normal water temperatures in the Equatorial Pacific Ocean, unlike El Niño which is associated with warmer than normal water temperatures. Both of these climate phenomena, which typically occur every 2-5 years, influence weather patterns throughout the world and often lead to extreme weather events. Last winter’s El Niño contributed to record-breaking rain and snowfall leading to severe flooding in some parts of the country, with record heat and drought in other parts of the country. Although La Niña is the opposite of El Niño, it also has the potential to bring weather extremes to parts of the nation.

“La Niña is in place and will strengthen and persist through the winter months, giving us a better understanding of what to expect between December and February,” said Mike Halpert, deputy director of the Climate Prediction Center – a division of the National Weather Service. “This is a good time for people to review the outlook and begin preparing for what winter may have in store.”

“Other climate factors will play a role in the winter weather at times across the country,” added Halpert. “Some of these factors, such as the North Atlantic Oscillation, are difficult to predict more than one to two weeks in advance. The NAO adds uncertainty to the forecast in the Northeast and Mid-Atlantic portions of the country.”

Regional highlights include:

Pacific Northwest:  Colder and wetter than average. La Niña often brings lower than average temperatures and increased mountain snow to the Pacific Northwest and western Montana during the winter months, which is good for the replenishment of water resources and winter recreation but can also lead to greater flooding and avalanche concerns. 

California and the Southwest: Warmer and drier than average. This will likely exacerbate drought conditions in these areas. All southern states are at risk of having above normal wildfire conditions starting this winter and lasting into the spring.