Deadly floods in Asia and early snowstorms in the United States signal the return of the La Niña weather phenomenon, a cooling of Pacific waters that could destabilize economies and trigger disasters around the world.
In recent La Niña years, global losses have ranged between $258 billion and $329 billion, according to Aon, a reinsurance broker and data analytics firm. Despite annual fluctuations in damage totals, the overall trajectory is undeniable: extreme weather conditions lead to increasing losses.
La Niña is often associated with droughts in California, Argentina and Brazil, as well as the devastating floods that recently hit Southeast Asia. These types of disasters have become an increasingly important factor in defining terms for insurers, farmers and energy providers.
La Niña can intensify droughts and torrential rains, fuel more active storms in the tropical Pacific, and strengthen hurricanes in the Atlantic. In previous episodes, this trend may have helped fuel the fires in Los Angeles in January and Hurricane Helene, which killed more than 250 people in the southern United States in 2024. Not all extreme events can be directly attributed to La Niña, but scientists say the characteristics are known.
“La Niña is like a traffic cop in the middle of rush hour, helping the flow of cars or weather systems in certain favored directions,” said Michelle L’Heureux, a meteorologist at the U.S. Climate Prediction Center.
She also compared her to the “conductor of a weather symphony” or a football quarterback directing the plays.
Although La Niña tends to follow a general pattern, L’Heureux points out that each event is different and other factors can influence the final outcome. La Niña generally doesn’t have a big influence on European weather, L’Heureux said.
The current La Niña is the fifth in six years, and part of a broader trend over the past quarter century where there are more La Niñas than El Niños (warming of Pacific waters). Scientists are still studying this change. Some suggest that climate change could influence the cycle, while others attribute it to natural variability, according to L’Heureux.
The ripple effects can even reach global markets. La Niña is often associated with lower yields of corn, rice and wheat, according to a study published in the journal Environmental Development.
Energy demand generally increases as colder temperatures set in in the northern United States, China and Japan, driving up fuel consumption and straining power utilities. These results can simultaneously increase the prices of some products while putting downward pressure on others.
Impact on Asia
Even a weak La Niña can leave deep scars. The weather is likely part of the combination that led to a series of tropical cyclones and devastating floods that killed more than 1,600 people and caused at least $20 billion in damage across South and Southeast Asia, according to a team of researchers who investigated the storm as part of an analysis of global weather attribution.
Floods that hit Vietnam and Thailand in November and December killed at least 500 people and caused more than $16 billion in damage and losses, according to data compiled by Bloomberg. Although La Niña’s role in these disasters is not certain, the pattern is consistent with its past behavior, L’Heureux said.
“La Niña’s contribution to above-average precipitation in Southeast Asia is costing lives and damaging infrastructure,” said Bill Hare, CEO of Climate Analytics.
Outlook for the United States
In North America, La Niña typically produces colder conditions and more snow in western Canada, the Pacific Northwest, the northern Rockies and the Great Lakes region, said Abby Frazier, a geography professor at Clark University.
Chicago has already recorded its snowiest November day on record this year, and central and northern New England saw more than 7 inches of snow in large areas, with some places reaching nearly 12 inches, according to the National Weather Service.
Global risks
Brazil, the world’s largest soy exporter, is monitoring signs that La Niña could reduce rainfall in parts of the southern producing regions. Forecasts indicate irregular rains in the center and south of the country, said meteorologist Marco Antonio dos Santos. He added that concerns are less for now as there are no signs of prolonged dry spells exceeding 20 days.
In Rio Grande do Sul, soybean planting is slightly delayed, but progressing, said agronomist Alencar Paulo Rugeri. “The concern is that we could have a drier December, but everything will depend on the intensity” of the drought, he added.
Weather conditions on the maritime continent are expected to become drier in December, while rains continue in Vietnam, according to forecasts from commercial meteorology company Ignitia.
Erratic rains can benefit some agricultural fields and harm others, but the risk arises when rains come out of season or fail to occur during crucial growing periods, “turning a professional activity into a lottery game with bad odds,” said Andreas Vallgren, Ignitia’s chief scientific officer.
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