El Niño shifts weather patterns across the globe by warming a large stretch of the central and eastern Pacific Ocean, which reshapes wind currents, storm tracks, and rainfall on nearly every continent. The effects vary by region, but the general pattern is consistent: wetter conditions in some areas, drought in others, and a measurable bump in global average temperatures of up to 0.2°C in a given year.
What Triggers an El Niño Event
Under normal conditions, strong easterly trade winds push warm surface water westward across the equatorial Pacific, piling it up near Australia and Southeast Asia. During El Niño, those trade winds weaken. Warm water that would normally stay in the western Pacific spreads eastward, raising sea surface temperatures across a vast area of open ocean.
Meteorologists track this using a patch of ocean called the Niño 3.4 region, which stretches from roughly 170°W to 120°W longitude. When the sea surface temperature there rises at least 0.5°C (0.9°F) above average for five consecutive three-month periods, the event officially qualifies as El Niño. That half-degree threshold sounds small, but spread across thousands of miles of ocean, it carries enormous energy, enough to rearrange atmospheric circulation patterns for months.
How the Jet Stream Shifts
The most important atmospheric change during El Niño is what happens to the Pacific jet stream, a fast-moving river of air roughly 30,000 feet above the surface that steers storms across North America. The warmer ocean water pumps extra heat and moisture into the atmosphere, which pulls the jet stream southward and extends it farther east than usual. The stronger the El Niño, the more dramatic this southward dip becomes.
This shift acts like a conveyor belt, funneling tropical moisture into new places. Instead of delivering storms to the Pacific Northwest (their usual winter destination), the redirected jet stream steers them into California and the southern tier of the United States. Very strong El Niño events push the storm track even farther south, sending heavy rain into Southern California while leaving Oregon and Washington unusually dry.
Winter Weather Across North America
The jet stream shift creates a split personality across the continent during winter. The southern United States, especially the Gulf Coast and Southeast, gets wetter than normal, with increased flooding risk. California often sees heavier rainfall and mountain snowpack, though the exact location depends on how strong the event is. Meanwhile, the northern U.S. and Canada tend to be warmer and drier than usual, since the storm track has moved away from them.
This pattern is consistent enough that forecasters use El Niño status as one of their primary tools for seasonal outlooks. It doesn’t guarantee specific weather on any given day, but it tilts the odds. A winter during a moderate to strong El Niño is significantly more likely to bring drought to the Pacific Northwest and flooding to Texas or Florida than a neutral year.
Drought in Australia and Southeast Asia
The same ocean warming that sends extra rain to the Americas pulls it away from the western Pacific. The heavy rainfall that normally sits over northern Australia and the Maritime Continent (Indonesia, Malaysia, the Philippines) migrates eastward toward the central Pacific, leaving those regions drier than normal from winter through spring.
Australia feels this acutely. Nine of the ten driest winter-to-spring periods on record for eastern Australia occurred during El Niño years. In the Murray-Darling Basin, the country’s most important agricultural region, winter and spring rainfall during El Niño events since 1900 has averaged 28% below the long-term mean. The severe droughts of 1982, 1994, 2002, 2006, and 2015 were all tied to El Niño. For a continent where agriculture depends heavily on seasonal rain, that deficit translates directly into crop losses and water restrictions.
Flooding in South America
Coastal Peru and Ecuador sit right next to the warming epicenter and experience some of El Niño’s most dramatic effects. Normally, cold, nutrient-rich water wells up along the South American coast. During El Niño, that upwelling weakens as warm water spreads eastward, raising coastal sea surface temperatures by several degrees. The warmer ocean heats the air above it, triggering deep atmospheric convection that produces intense rainfall over a region that is typically arid.
The results can be devastating. Flooding, landslides, and infrastructure damage hit coastal communities hard. South American fishermen first noticed these periodic warm-water events in the 1600s and named the phenomenon El Niño de Navidad (the Christ Child) because it typically peaks around December. In 2023, an extreme coastal El Niño brought record rainfall to Peru and Ecuador, along with a surge in mosquito-borne diseases like dengue.
How El Niño Changes Hurricane Seasons
El Niño has opposite effects on hurricanes depending on which ocean basin you’re watching. In the Atlantic, it suppresses hurricane activity. In the central and eastern Pacific, it enhances it.
The mechanism comes down to wind shear, the difference in wind speed and direction between the lower and upper atmosphere. Hurricanes need calm, vertically aligned conditions to organize and strengthen. During El Niño, the altered jet stream creates stronger upper-level westerly winds over the Atlantic, which increases wind shear and tears developing storms apart before they can intensify. At the same time, weaker upper-level winds over the central and eastern Pacific reduce shear there, giving tropical cyclones a more favorable environment to grow.
This is why Atlantic hurricane season forecasts always factor in the current ENSO state. An El Niño year typically produces fewer named storms in the Atlantic, while La Niña years tend to be more active.
Effects on Global Food Production
Because El Niño rearranges rainfall patterns across the tropics and subtropics, it directly affects the world’s major growing regions. Research spanning two decades has found that El Niño reduces yields of wheat, rice, and maize globally, while slightly boosting soybean production. La Niña tends to have the opposite effect on wheat and rice.
The stakes are highest in Asia, which produces 90% of the world’s rice supply and depends heavily on predictable monsoon rains. Thailand’s rainfed rice crop is especially sensitive to ENSO shifts. Cacao, coffee, and cassava are also vulnerable. These disruptions ripple through global commodity markets, contributing to higher food prices and, in the worst cases, food insecurity in regions that depend on staple crop imports.
Collapse of Pacific Fisheries
The same coastal warming that brings floods to Peru devastates one of the world’s most productive marine ecosystems. Normally, cold water rising from the deep ocean along the Peruvian coast carries nutrients that feed massive blooms of phytoplankton, the base of the food chain. During El Niño, waves of warm water from the equator deepen the layer where those nutrients sit, so even though winds still drive water upward, what reaches the surface is depleted. During the powerful 1997-1998 El Niño, sea surface temperatures off Peru rose by roughly 3°C above normal.
The drop in phytoplankton cascades upward through the food web. Peruvian anchovy populations, one of the largest fisheries on Earth, crash as their food supply disappears. Seabirds, marine mammals, and other predators that depend on anchovies suffer high mortality. The fishery disruption can last well beyond the El Niño event itself, since fish populations take time to recover even after ocean conditions return to normal.
Global Temperature Bump
Beyond regional weather shifts, El Niño raises the planet’s average temperature. The vast pool of warm surface water releases extra heat into the atmosphere, boosting global averages by up to 0.2°C over the course of a year. That may not sound like much, but it is significant in a climate system where long-term warming trends are measured in tenths of a degree per decade. The hottest years on record frequently coincide with strong El Niño events, as the natural warming stacks on top of the background trend from greenhouse gas emissions.
El Niño events recur every two to seven years and typically peak between November and January. As of early 2026, the Pacific is in a La Niña phase (the cool counterpart to El Niño), with a transition to neutral conditions expected by spring 2026. Forecasters see roughly a 50-60% chance of El Niño forming by late summer 2026, though predictions made this far in advance carry substantial uncertainty.