La Niña could be coming soon. Here's what this means for 2024-25 winter weather

The National Oceanic and Atmospheric Administration's Climate Prediction Center estimates there is a 60% chance of a weak La Niña event developing this fall and could last through March.

La Niña is part of a natural climate cycle that can cause extreme weather events around the world, with impacts varying from place to place.

While there is no guarantee as to how this La Niña will play out, there are some general trends. Experts say northern parts of South America could see more rain than usual. The southern regions of the U.S. and parts of Mexico could be drier than average. The northern part of the U.S. and southern Canada could be wetter than average.

Watch FOX 11 News on November 15 for Chief Meteorologist Patrick Powell's winter forecast.

La Niña is the cool phase of the El Niño-Southern Oscillation, a naturally occurring global climate pattern that brings changes in wind and ocean temperatures in the Pacific and can lead to extreme weather conditions around the world.

El Niño is the warm phase and occurs when the trade winds that normally blow across the Pacific toward Asia weaken, allowing warm seawater to accumulate on the western edge of South America. But during La Niña, trade winds intensify and cold water from the ocean depths rises, resulting in cooler than average ocean temperatures in the Eastern Pacific.

These cold ocean temperatures and changes in the atmosphere affect the position of the jet stream — a narrow band of fast-moving air that flows around the planet from west to east — by pushing it northward. The jet stream sits over the ocean and can harness its moisture, influencing the path of storms and increasing precipitation.

Most recently, Earth experienced a “triple-dip” La Niña event from 2020 to 2023. “We had three consecutive winters where we had La Niña conditions, which was unusual since the only other case of such an event occurred in 1973 to 1976,” said Michelle L'Heureux, a climate scientist at NOAA . L'Heureux said La Niñas tend to last longer and occur more frequently than El Niño events.

“It's unusual, although it's not unprecedented,” Ben Cook, a climate scientist at NASA's Goddard Institute for Space Studies, affiliated with Columbia University, said of predicting a possible La Niña this year.

Cook noted that the frequency of La Niña events can be stressful for regions that have recently struggled with drought, such as East Africa. “If we move on to another La Niña event, that will mean a continuation of these really bad conditions, so to speak.”

Effects of La Niña weather

La Niña's influence on weather varies depending on location and time of year, L'Heureux said. Parts of South America, such as eastern Argentina, may be dryer than average, while Colombia, Venezuela and northern parts of Brazil may be wetter than normal.

“It depends exactly where you are. “That's partly because there is a monsoon cycle, a wet season and a dry season, that runs through Central America and South America, so La Niña essentially changes the intensity and placement of those monsoon cycles,” L “Heureux explained.

In the U.S., the Northeast and Ohio Valley typically experience wetter conditions with an active storm track because of the position of the jet stream, said Samantha Borisoff, a climate scientist at NOAA's Northeast Regional Climate Center at Cornell University.

The ripple of the jet stream may also lead to more frequent cold outbreaks, particularly in the central US. Borisoff said snowfall is difficult to predict and depends heavily on the storm and the direction it takes, but noted that New England, New York and the Great Lakes region tend to see more snow in La Niña winters, but that is not a guarantee. The southern and southeastern regions of the U.S. are further from the active storm track and tend to be drier and warmer than normal.

La Niña, El Niño and climate change

Scientists say the connection between climate change and La Niña and El Niño is not entirely clear.

Paul Roundy, a climate scientist at the University of Albany, said climate models tend to point to more frequent El Niños and less frequent La Niñas, but not all models agree. Computer models also have difficulty separating the normal fluctuations in El Niño and La Niña phases from the warming influence of climate change on the oceans and atmosphere.

“I wouldn’t conclude from that that climate change isn’t actually leading to more El Niño events,” Roundy said. “It's just that nature itself has such strong fluctuations. So we may see multiple La Niña events, and maybe in 40 or 50 years we will see the opposite.”

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