A newly emerged La Niña weather pattern in the Pacific Ocean is triggering fresh concerns for drought in California, Brazil, and Argentina, while setting the stage for a colder winter in the U.S. Midwest and milder conditions along the East Coast, according to the latest forecast from the U.S. Climate Prediction Center.

The phenomenon, which began developing in September 2025, is expected to persist through February 2026, impacting key agricultural regions and energy markets across the Americas. Though this La Niña event is predicted to be weak, forecasters warn it may still alter global atmospheric circulation enough to influence weather-dependent sectors.

La Niña forms when surface waters in the equatorial Pacific Ocean cool below average and affect the atmosphere's circulation, shifting jet streams and storm patterns. These shifts often reduce rainfall across Southern California and South America's southern agricultural belts, increasing the potential for yield-reducing droughts in Brazil's soybean-growing regions and Argentina's corn belt.

"There's a strong chance this La Niña will be weak," said Michelle L'Heureux, forecaster with the Climate Prediction Center. "But even weak events can have meaningful impacts on global agriculture and energy demand, especially when they persist over multiple months."

In the U.S., the forecast indicates colder-than-average temperatures across the Upper Midwest and Great Plains, which could increase heating fuel demand. Conversely, New York and much of the East Coast may experience a milder winter, with more rain than snow in typical cold-season storms. Historical patterns suggest a shifting storm track could bring more inland precipitation but fewer coastal snow events.

La Niña events are closely watched by commodity markets, especially for their impact on South American crop yields, natural gas consumption, and wheat and corn exports. A prolonged dry season could challenge planting and early development of key crops, particularly in southern Brazil, where La Niña is often associated with below-average rainfall during the austral summer.

The pattern is part of the broader El Niño-Southern Oscillation (ENSO) cycle, which alternates between La Niña's cooler conditions and the warmer El Niño phases. According to L'Heureux, La Niña conditions have occurred nearly twice as often as El Niño since 1980, making this cool phase an increasingly dominant force in seasonal climate variability.

While this year's event may not reach the strength of prior La Niñas, the persistence of such patterns can amplify long-term climate effects, including shifting rainfall patterns, increasing volatility in crop forecasts, and stressing global supply chains. For producers, co-ops, and ag market analysts, the coming months will demand close monitoring of soil moisture, planting conditions, and early yield potential in Brazil and Argentina.