El Niño causes a cascade of disruptions across weather, ecosystems, agriculture, and human health on every continent. It begins as an ocean warming event in the tropical Pacific but ripples outward, shifting rainfall patterns, suppressing fish populations, bleaching coral reefs, and costing the global economy trillions of dollars. Here’s how it works and what it does.
How El Niño Starts
Under normal conditions, strong trade winds blow east to west across the equatorial Pacific, pushing warm surface water toward Southeast Asia and Australia. That movement pulls cold, nutrient-rich water up from the deep ocean along the western coast of South America, a process called upwelling.
During El Niño, those trade winds weaken. The ocean current that draws surface water westward slows down, and warm water sloshes back east toward the Americas. The boundary between warm surface water and cold deep water (the thermocline) flattens out, and upwelling weakens or stops entirely. The result is a massive pool of unusually warm water sitting in the central and eastern Pacific, sometimes persisting for 12 to 18 months. That warm water reshapes atmospheric circulation patterns worldwide.
Shifts in Rainfall and Drought
The warm water displaced eastward doesn’t just heat the ocean surface. It pumps extra moisture and energy into the atmosphere above it, pulling storm tracks and jet streams out of their usual positions. The west coast of the Americas tends to get heavier rainfall and flooding, while Southeast Asia, Australia, and parts of southern Africa experience drier conditions. Peru and Ecuador can see catastrophic flooding, while Indonesia and northern Australia face prolonged drought.
In the United States, El Niño typically brings a wetter, stormier winter to the southern tier of states, from California through the Gulf Coast. The northern U.S. and Canada often see milder winters. These shifts aren’t uniform every time, but the overall pattern is consistent enough that forecasters use El Niño status to shape seasonal outlooks months in advance.
Fewer Atlantic Hurricanes, More Pacific Ones
El Niño reshapes hurricane seasons in opposite directions depending on the ocean basin. In the Atlantic, it suppresses hurricane activity. The mechanism is vertical wind shear: El Niño strengthens upper-level westerly winds over the Atlantic while reinforcing lower-level easterly trade winds. That mismatch tears apart developing storms before they can organize. El Niño also increases sinking air motion over the Atlantic, making the atmosphere more stable and less hospitable to hurricanes.
In the central and eastern Pacific, the opposite happens. El Niño weakens upper-level winds, reduces wind shear, and creates conditions that favor stronger and more frequent hurricanes. So a strong El Niño year often means a quiet Atlantic hurricane season paired with an unusually active Pacific one.
Collapse of Marine Food Chains
When upwelling weakens along the coast of South America, the supply of cold, nutrient-rich water that feeds the base of the marine food web shuts down. Microscopic algae that depend on those nutrients decline, followed by the small fish and zooplankton that eat them, followed by everything up the chain.
The Peruvian anchovy fishery, one of the world’s largest, is especially vulnerable. Anchovy populations crash during strong El Niño events as the fish either migrate to find cooler water or simply can’t find enough food. Along the U.S. West Coast, El Niño delays the annual spring upwelling that fuels productivity in the California Current. Once upwelling resumes after El Niño fades, recovery can be rapid. Following one recent event, nutrient-rich waters returned strongly enough to support abundant anchovy and krill populations and boost production of young hake and juvenile rockfish. But the gap between collapse and recovery can devastate fishing communities that depend on consistent seasons.
Coral Bleaching on a Massive Scale
Warmer ocean temperatures during El Niño push coral reefs past their thermal tolerance. Corals expel the symbiotic algae that provide them with food and color, turning white in a process called bleaching. If temperatures stay elevated too long, the corals starve and die.
The damage during major El Niño events has been staggering. During the 1982-83 event, some locations in the eastern Pacific lost up to 95% of their coral, and certain sites in Indonesia experienced nearly 100% local coral mortality. The 1997-98 event killed up to 90% of corals on individual shallow reefs in the Indian Ocean. These aren’t temporary setbacks. Coral reefs can take decades to recover, and repeated bleaching events from successive El Niños can prevent full recovery entirely.
Wildfires in Indonesia, Australia, and Beyond
The drought conditions El Niño brings to Southeast Asia and Australia create prime conditions for large-scale wildfires. During El Niño events, global fire emissions increase by roughly 6% to 20%, with the worst impacts concentrated in Indonesia, North America, and Australia.
The air quality consequences are severe. Fire-related fine particle pollution (PM2.5) rises by 28% to 71% in Indonesia during El Niño years, 49% to 117% in North America, and 18% to 43% in Australia. Indonesia’s peatland fires are particularly dangerous: dried-out peat burns underground for weeks, producing thick haze that blankets the region and causes respiratory crises across Southeast Asia.
Crop Yields and Food Prices
El Niño’s reach extends directly to farmland. Altered rainfall and temperature patterns reduce yields for several staple crops worldwide. On average, El Niño cuts global wheat yields by about 1.3%, rice yields by 1.3%, and maize yields by 0.4%. Soybean is the exception, with yields actually increasing by about 1.9% during El Niño years.
Those percentages sound small, but they represent enormous volumes of food. Roughly 13% of the world’s rice-growing areas and 12% of maize-growing areas show significantly reduced harvests during El Niño. The effects aren’t distributed evenly: regions that depend on rain-fed agriculture in Southeast Asia and sub-Saharan Africa bear the heaviest burden, while some temperate growing regions benefit from milder conditions. The uneven impact tends to drive up global commodity prices, hitting food-importing nations hardest.
Disease Outbreaks
The warmer, wetter conditions El Niño creates in many tropical regions are ideal for disease-carrying mosquitoes and other vectors. Mosquitoes breed more prolifically in standing water left by heavy rains, survive longer in warmer temperatures, and travel farther. Research has linked El Niño phases to increased transmission of dengue, Zika, chikungunya, malaria, and several other vector-borne diseases. Flooding also contaminates water supplies, raising the risk of waterborne diseases like cholera and leptospirosis.
These health impacts tend to hit regions with limited public health infrastructure the hardest. Communities already vulnerable to infectious disease outbreaks face compounded risk when El Niño simultaneously disrupts food production and displaces populations through flooding.
Trillions in Economic Losses
A study published in Science estimated that the 1982-83 El Niño event caused $4.1 trillion in global income losses, and the 1997-98 event caused $5.7 trillion. These aren’t just the costs of immediate disaster relief. El Niño persistently reduces country-level economic growth, meaning the damage compounds over years as affected economies grow more slowly than they otherwise would have.
Looking ahead, projections suggest that increasing El Niño intensity driven by climate change could cause $84 trillion in cumulative economic losses over the 21st century under current emissions pledges. Developing nations in the tropics, where El Niño’s weather impacts are strongest and economic buffers are thinnest, absorb a disproportionate share of the damage.
Current ENSO Status
As of early 2026, the Pacific is in a La Niña phase, with below-average sea surface temperatures in the east-central equatorial Pacific. NOAA’s Climate Prediction Center expects a transition to neutral conditions within the next month, with neutral conditions favored through May to July 2026. By June to August 2026, there is a 62% chance that El Niño will emerge, potentially persisting through the end of the year. That timeline gives communities, fisheries, and agricultural planners several months to prepare for the next round of El Niño impacts.