El Niño 2026: High probability confirmed, but impacts remain uncertain

The Pacific Ocean is warming faster than usual, and climate models are nearly certain it will trigger El Niño conditions sometime between now and early 2027. The probability sits at 82 percent for the May-to-July window, climbing to 96 percent by winter. In Brazil, this news has put civil defense agencies, agricultural planners, and state governments on alert. But the certainty of the phenomenon itself masks a deeper uncertainty: what it will actually do when it arrives.

El Niño is not mysterious in its mechanics. Normally, trade winds push warm Pacific water westward toward Asia and Oceania. When those winds weaken or reverse, warm water spreads eastward across the equatorial Pacific, disrupting atmospheric circulation patterns that influence rainfall and temperature thousands of miles away. In Brazil's south, the typical effect is more rain than average—sometimes far more. In the north and northeast, the opposite happens: less rain, more heat, greater fire risk. The center-west and southeast experience more variable impacts. This much is established science, confirmed by decades of observation.

What remains genuinely uncertain is the intensity. Some models suggest a moderate-to-strong event. Others point toward a strong or very strong episode—sometimes called a "Super El Niño." The difference matters. A 2015-2016 El Niño brought significant flooding to Rio Grande do Sul but did not approach the scale of the catastrophic 2024 floods that killed over 170 people and displaced thousands. Current projections lean toward conditions comparable to 2015-2016, not 2024. But the Brazilian government has been careful not to rule anything out. A technical note from four major research institutions—INPE, INMET, Funceme, and Censipam—confirmed high probability of El Niño establishment in the second half of 2026, possibly persisting into early 2027, with a 83 percent chance that Pacific temperatures will run 1.5 to 2 degrees Celsius above normal.

The gap between "above-average rainfall" and "catastrophic flood" is where most of the confusion lives. Seasonal forecasts describe regional trends over months or quarters. They cannot predict which neighborhoods will flood, which rivers will overflow, or on what date. Those outcomes depend on a tangle of variables: atmospheric blocking patterns, stationary fronts, extratropical cyclones, Atlantic Ocean temperatures, soil saturation, river conditions, urban drainage capacity, settlement patterns in flood-prone areas, and the speed of local emergency response. A city can experience above-average rain and suffer no major flooding if the precipitation is spread across weeks rather than concentrated in days. Conversely, a single intense storm system can cause devastation regardless of seasonal forecasts.

Rio Grande do Sul has begun preparing anyway. The state government identified 60 municipalities with the highest historical exposure to extreme weather and is holding targeted meetings to present customized vulnerability assessments and align contingency protocols. All 497 municipalities in the state maintain structured disaster response plans. The state has quadrupled its technical civil defense staff, deployed one weather radar in Porto Alegre, and contracted three more with installation expected in coming months. Hydrodynamic modeling is being used to project river behavior and map flood extents at different water levels for the 60 most vulnerable cities.

When Agora RS contacted 20 municipalities across the state to assess their own preparedness, only two responded: Santa Maria and Rio Grande. Santa Maria reported updated contingency plans, a new digital portal for risk assessment and volunteer coordination, and six pre-mapped shelters with capacity for pets. The city advanced from a C-level to A-level municipal capacity rating between 2024 and 2025. Rio Grande is finalizing an updated contingency plan using digital twin technology from the Federal University of Rio Grande to simulate flood scenarios and predict affected areas. Both cities are conducting evacuation drills in coming weeks. The silence from the other 18 municipalities is itself a data point—one that suggests preparedness remains uneven across the state.

Agriculture is watching closely too. Excess rain in the south can damage grain quality, increase disease pressure, delay harvests, and compress planting windows. Rice producers in Rio Grande do Sul have already begun factoring El Niño into their 2026-2027 planning. In the center-west, the concern is rainfall irregularity and temperature swings that disrupt uniform production. In the north and parts of the northeast, water stress looms. The sector understands that El Niño is not a single event but a cascade of regional consequences, each requiring different preparation.

What is certain is that the Pacific is warming and El Niño is coming. What remains open is how hard it will hit, where, and when. That uncertainty is not an excuse for inaction—it is precisely why the months ahead matter. The state and its municipalities are building capacity now, before the system fully forms. Whether that preparation proves adequate will depend on factors no forecast can yet pin down.