(Bloomberg) — Deadly floods in Asia and early snowstorms in the United States indicate the return of a La Niña, a cooling of Pacific waters that could destabilize economies and trigger disasters around the world.
In recent La Niña years, global losses ranged between $258 billion and $329 billion, according to Aon, a reinsurance broker and data analytics company. Despite annual fluctuations in damage totals, the overall trajectory is clear: extreme weather is driving up losses. The La Niña phenomenon is often associated with droughts in California, Argentina and Brazil, and the destructive floods that recently swept Southeast Asia. These types of catastrophes have become an increasingly important factor in defining terms for insurers, farmers and energy suppliers.
La Niña can intensify both droughts and heavy rains, fuel more active storms in the tropical Pacific and strengthen hurricanes in the Atlantic. In past episodes, the pattern may have contributed to the wildfires in Los Angeles in January and Hurricane Helene, which killed more than 250 people in the southern US in 2024. Not every extreme event can be directly linked to La Niña, but scientists say the hallmarks are familiar.
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“La Niña is like a traffic cop in the middle of rush hour, helping the flow of cars or weather systems in certain preferred directions,” said Michelle L’Heureux, a meteorologist at the U.S. Climate Prediction Center. She also compared her to “a conductor of a symphony of time” or an American football quarterback calling 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 typically doesn’t have a big influence on Europe’s climate, L’Heureux said.
The current La Niña is the fifth in six years, part of a larger trend of more La Niñas than El Niños (the warming of Pacific waters) over the last 25 years. Scientists are still studying this change. Some suggest that climate change may be influencing the cycle, while others attribute it to natural variability, L’Heureux said.
The ripple effects could reach global markets. La Niña is often associated with lower yields of corn, rice and wheat, according to research published in the journal Environmental Development. Demand for energy generally increases as colder temperatures in the northern US, China and Japan increase fuel consumption and put pressure on utilities. These effects can simultaneously raise prices of some commodities while putting pressure on others.
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The impact on Asia
Even a weak La Niña can leave a heavy mark. The weather pattern was likely part of the recipe for a string of tropical cyclones and destructive floods that killed more than 1,600 people and caused at least $20 billion in losses in South and Southeast Asia, according to a team of researchers who investigated the storm as part of a World Weather Attribution analysis.
Floods in 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. While La Niña’s role in these disasters is not certain, the pattern is consistent with its past behavior, L’Heureux said.
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“La Niña’s contribution to above-normal rainfall in Southeast Asia is costing lives and damaging infrastructure,” said Bill Hare, CEO of Climate Analytics.
China faces its own risks. Below-average temperatures could threaten winter wheat production, said Luiz Roque, market intelligence coordinator at Hedgepoint Global Markets. This threat, as well as impacts in other regions, will likely be mitigated by the weakness of the current La Niña.
Palm oil producers in Southeast Asia could see more intense rain disrupt harvesting and transportation, affecting monthly production and oil extraction rates, said Kang Wei Cheang, an agricultural broker at StoneX Group Inc. in Singapore. At the same time, increased humidity can benefit plantations in around five to 12 months, promoting tree recovery and cluster formation.
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Perspectives in the USA
In North America, La Niña typically brings colder, snowier conditions in western Canada, the Pacific Northwest, the Northern Rockies and the Great Lakes region, said Abby Frazier, a geography professor at Clark University. Chicago already recorded its snowiest November day on record this year, and central and northern New England saw more than seven inches of snow in large areas, with some places getting nearly a foot, according to the National Weather Service.
By measuring heating degree days, a method for tracking temperature-driven energy demand, November was colder than last year but warmer than the 10-year average, said Matt Rogers, president of the Commodity Weather Group. The densely populated Northeastern US was colder than normal.
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The colder, snowier conditions in the northern U.S. are being helped by La Niña, said Paul Pastelok, long-range meteorologist at AccuWeather Inc. “It’s helping, it’s not the only reason, but it’s helping,” he said.
La Niña’s influence in the U.S. Southwest generally tends to trigger drought, a pattern that could extend into Southern California, said Clark University’s Frazier. However, there are cases where other weather patterns, such as intense maritime heatwaves in the Pacific, may contradict expectations, according to Jennifer Francis, a climate scientist at the Woodwell Climate Research Center.
“A prime example was the winter of 2022-23, the third in a row with La Niña conditions,” Francis said. “That winter was the wettest in California in more than two decades.”
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Global risks
Brazil, the world’s largest soybean exporter, is watching for signs that La Niña could reduce rainfall in parts of the country’s southern producing regions. The forecast indicates irregular rains in central and southern Brazil, meteorologist Marco Antonio dos Santos said, adding that concerns are less for now because there are no signs of prolonged dry periods longer than 20 days.
In the country’s southernmost state, Rio Grande do Sul, soybean planting is slightly delayed but underway, said agronomist Alencar Paulo Rugeri. “The tension is that we may have a drier December, but everything will depend on the intensity” of the drought, he added.
Conditions in the Maritime Continent are expected to dry out in December, while rains continue in Vietnam, according to forecasts from commercial service Ignitia.
Irregular rains can help some crops and harm others, but the risk occurs when precipitation arrives out of season or skips key growth periods, “turning a professional activity into a lottery game with little chance,” said Andreas Vallgren, scientific director at Ignitia.
The climate layer
Although La Niña is a natural cycle, its impacts are “being modified and amplified by global warming,” according to Climate Analytics’ Hare.
“While they are distinct from the long-term warming trends caused by human activities — especially the continued burning of fossil fuels, which is driving devastating changes in temperature and precipitation extremes around the world — they modulate and, to some extent, exacerbate underlying global warming trends,” Hare said.
As for the current La Niña, it is likely peaking now, or will be in the coming weeks, and conditions in the equatorial Pacific should return to neutral, he said. Even if the Pacific returns to a more normal state, that doesn’t mean global climate change will end. La Niña conditions could persist for months.
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