La Niña’s fingerprints are all over winter weather forecasts

After a short absence, climate troublemaker La Niña is back, and forecasters say it could have a big impact on the winter weather outlook.

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 Ocean. La Niña is marked by cooler-than-average ocean water in the region.

Those subtle changes can have big ripple effects across the globe’s climate, with the cycle at times upping the chances for rain, drought, hurricanes and other chaos. The effects vary drastically by region, even within the U.S.

Impacts from a typical La Niña cut across the continental U.S., having opposite effects in the south and north – and causing unpredictability in the heavily populated Northeast corridor.

While La Niña usually only comes every few years, it made an appearance in winter 2024-2025 for several months as well.

The latest La Niña is expected to be relatively weak and short-lived, but still is expected to be a major factor in weather patterns over the winter.

Jon Gottschalck, chief of the operational prediction branch of the Climate Prediction Center, told USA Today, “even though it is considered a weak event, likely shorter than normal in duration, its impact is likely to be strongest during the winter season and so plays a large role in the outlooks.”

Here’s what to know.

Is La Niña dangerous?

La Niña itself – just a cooling of sea water in the Pacific Ocean – is not dangerous. However, the weather and climate impacts that result from La Nina can certainly be dangerous. This is due to its association with a more active Atlantic hurricane season, an increased threat of wildfires in some regions, and the chances for disastrous floods or other extreme weather.

How could La Niña impact hurricane season?

AccuWeather lead hurricane expert Alex DaSilva recently said in an online forecast that the emergence of La Niña “favors an active end to the hurricane season.”

So far, as of Oct. 21, 13 named storms have formed in the Atlantic, of which four were hurricanes. An average season sees 14 storms and seven hurricanes.

Specifically, November tropical storms could be affected by La Niña, according to Matthew Rosencrans, lead hurricane seasonal forecaster with the National Oceanic and Atmospheric Administration.

“La Niña conditions are associated with more activity (double the amount) in November when compared to ENSO Neutral and especially when compared to Novembers with El Niño conditions,” he said in an e-mail to USA Today.

When a La Niña phase occurs, less wind shear occurs in the regions of the Atlantic basin where tropical weather develops, increasing the potential for more storms, AccuWeather said.

Hurricane season officially ends Nov. 30.

How will La Niña impact winter weather?

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.

In the East, the northern branch of the jet stream tends to carry faster-moving, less intense storms, which can mean snowfall near or even below average, with temperatures closer to seasonal norms, AccuWeather said.

How do scientists know La Niña is here?

Scientists from NOAA and other agencies use a variety of tools and techniques to monitor and forecast temperature changes in the Pacific Ocean and the impact of those changes on global weather patterns, according to a NOAA report. In the tropical Pacific Ocean, La Niña and El Niño are detected by many methods, including satellites, moored buoys, drifting buoys, sea level analysis and expendable buoys, according to NOAA.

Why is La Niña important?

Good La Niña intelligence means better predictions of the potential for extreme climate episodes like floods and droughts, which could save the United States billions of dollars in damage costs, NOAA reports.

“Predicting the onset of a warm or cold phase is critical in helping water, energy and transportation managers, and farmers plan for, avoid or mitigate potential losses. Advances in improved climate predictions will also result in significantly enhanced economic opportunities, particularly for the national agriculture, fishing, forestry and energy sectors, as well as social benefits,” NOAA said.

In addition, “seasonal forecasts for El Niño and La Niña and their associated impacts on our weather are an important climate intelligence tool,” said World Meteorological Organization secretary-general Celeste Saulo, in a recent statement.

“They translate into millions of dollars of economic savings for key sectors like agriculture, energy, health and transport and have saved thousands of lives when used to guide preparedness and response actions,” she added.