Early signs of a possible La Niña fall and winter are emerging in some climate models, federal forecasters announced July 10.
La Niña is a part of a natural climate cycle officially known as El Niño – Southern Oscillation, called ENSO by scientists. The cycle swings between warmer and cooler seawater in a region along the equator in the tropical Pacific. La Niña is marked by cooler-than-average ocean water in the region.
It is one of the main drivers of weather in the United States, especially during the late fall, winter and early spring. It’s the opposite of the more well-known El Niño, which occurs when Pacific Ocean water is at least 0.9 degree warmer than average for three months.
La Niña and El Niño typically have minimal impact on summer weather in the United States, other than some effects on hurricanes. Winter is the one season when they have the most impact.
A typical La Niña winter in the United States brings cold and snow to the Northwest and unusually dry conditions to most of the Southern states, according to the Climate Prediction Center. The Southeast and mid-Atlantic also tend to see higher-than-average temperatures during a La Niña winter.
Meanwhile, New England and the Upper Midwest, including New York, tend to see lower-than-average temperatures, the Weather Channel said.
More: Will a hurricane impact your state in 2025? Odds get an update.
Map shows what a La Niña could mean for winter 2025-2026
The typical impacts of a La Niña winter in North America include a wetter, colder winter in parts of the northern United States and a drier, warmer winter in parts of the southern United States.
What is La Niña?
La Niña is a natural climate pattern marked by cooler-than-average seawater in the central and eastern Pacific Ocean. When the water cools at least 0.9 degree Fahrenheit below average for three straight months, a La Niña is declared.
“While this may sound like a small change in temperature, it can cause significant changes in the weather patterns around the globe,” AccuWeather meteorologist Brian Lada said.
Could the possible La Niña affect the hurricane season?
In general, La Niña conditions favor hurricane development in the Atlantic basin, which includes the Caribbean Sea and the Gulf of America, formerly known as the Gulf of Mexico. This is because during La Niña, the strong storm-killing winds known as wind shear relax across the Atlantic basin, allowing hurricanes to more easily develop.
Hurricane researcher Phil Klotzbach of Colorado State University, in a July 10 email to USA TODAY, explained that “while Caribbean shear has been quite strong in June and is likely to remain strong throughout most of July, the potential trend more towards cool neutral (or even weak La Niña) later in the season may result in lower shear in the Caribbean later in the season.”
The lower the wind shear, the greater the chance for hurricane development in the Atlantic basin.
But the status of ENSO is only part of the hurricane puzzle: Twenty years ago, in 2005, for instance, ENSO-neutral conditions also occurred in the Pacific ‒ and that year spawned the infamously destructive hurricanes Katrina and Rita, the National Weather Service said in an online report.
How likely is a La Niña winter?
Right now, it appears to be a toss-up.
While so-called “ENSO-neutral” conditions are most likely through the late summer, thereafter, chances of La Niña conditions increase into the fall and winter 2025-26, forecasters from the Climate Prediction Center (CPC) said July 10. In fact, one climate model used by the CPC – the North American Multi-Model Ensemble – “favors the onset of La Niña conditions during the Northern Hemisphere fall,” the CPC said in its monthly update.
Japan’s weather bureau also announced July 10 that there is a 40% chance of La Niña emerging in the fall.
Overall, the CPC said the chances for La Niña remain comparable to the likelihood of ENSO-neutral continuing.
What is ENSO-neutral?
ENSO-neutral means neither El Niño (warmer waters) nor La Niña (cooler waters) conditions are dominant in the Pacific. While El Niño and La Niña have expected impacts on global seasonal weather and climate, what about neutral?
“ENSO-neutral doesn’t mean we expect upcoming seasonal rain, snow, and temperature to be close to average,” writes Emily Becker in the CPC’s ENSO blog. “Rather, during neutral, we don’t have the same predictive information that El Niño and La Niña’s atmospheric changes provide, making upcoming patterns harder to predict very far in advance.”
Contributing: Reuters
This article originally appeared on USA TODAY: 2025 La Niña forecast says major shift may be brewing
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