El Niño vs. La Niña: what each phase means for North American growing seasons

For three winters running, from 2020 to early 2023, the tropical Pacific sat in La Niña, an unusually long spell that NOAA declared over in March. By June it had flipped. NOAA’s Climate Prediction Center announced El Niño conditions on June 8, and its September outlook gave a better than 95 percent chance that El Niño would last through the winter, with about a 71 percent chance of a strong event. For anyone planning a garden, an orchard or a winter crop, that shifts the odds for the coming months.

What the two phases are

El Niño and La Niña are the warm and cool phases of the El Niño Southern Oscillation, or ENSO, a pattern in the ocean and atmosphere of the tropical Pacific. In El Niño, the surface waters of the central and eastern equatorial Pacific run warmer than average; NOAA’s working threshold is 0.5 degrees Celsius above normal in the key monitoring region, together with a matching response in the winds and rainfall above it. La Niña is the reverse: cooler water and stronger trade winds.

According to NOAA’s climate.gov, the system swings between the phases every three to seven years on average. An episode usually lasts nine to twelve months, though La Niña often hangs on for two years or more, as it just did. In between come neutral years, when neither phase is present.

How a Pacific pattern reaches a garden in Ohio

The warm water moves the tropical rainfall, and the rainfall moves the jet streams that steer storms across North America. During El Niño the Pacific jet tends to stretch east and run farther south, carrying storms across the southern United States. During La Niña it tends to buckle north, steering storms into the Pacific Northwest and the Ohio Valley and leaving the south dry. The effect on North America is strongest from December through February and can linger into spring.

The typical El Niño winter

The southern tier of states, from California to the Carolinas, tends to be cooler and wetter than average. The northern states, southern Alaska and the Pacific Northwest tend to be warmer, and the Pacific Northwest and the Ohio Valley drier. Western and central Canada usually get milder winters with less snow.

For growers, the southern moisture is mostly welcome. It recharges soil for winter wheat and pasture in the southern Plains and fills reservoirs in the Southwest. In Florida and along the Gulf Coast, a wet, cloudy, cool winter slows winter vegetables and raises disease pressure. In the Northwest and northern Rockies, a warm, dry winter can mean a thin snowpack, and in those valleys snowmelt is the irrigation supply for the following summer.

The typical La Niña winter

Roughly the opposite. The southern tier tends to be warmer and drier, which raises drought risk from southern California across Texas to Florida. The Pacific Northwest, southern Alaska and the Ohio and upper Mississippi valleys tend to be wetter, and the northern Plains colder. The record Texas drought of 2011 followed a strong La Niña winter, and the recent three-year La Niña kept much of the West and the southern Plains short of water.

ENSO also affects the hurricane season. El Niño tends to suppress Atlantic hurricanes and favor eastern Pacific ones; La Niña does the reverse.

Odds, not promises

These are tendencies. NOAA notes that a “typical” impact may show up in as many as 80 percent of events or as few as 40 percent, and no two events are alike. The strong El Niño of 2015 to 2016 was expected to soak southern California and instead left it drier than normal. ENSO also says much less about summer weather in the United States, so it is a better guide to winter water supply than to the next growing season’s heat.

The practical use is in preparation. In a region tilted toward a dry winter, plan to water trees and perennials through the dormant season, mulch beds and catch every rain that does fall. Where a wet winter is likely, check drainage, raise beds that sit wet, and hold off on planting into cold, waterlogged soil. The Climate Prediction Center updates its ENSO outlook each month and publishes seasonal temperature and rainfall outlooks for the months ahead.

Since then, the 2023 to 2024 El Niño peaked as a strong event and faded in spring 2024, a brief and weak La Niña came and went over the winter of 2024 to 2025, and in its September 2026 discussion the Climate Prediction Center reported a new El Niño strengthening toward a very strong event for the winter of 2026 to 2027.