El Niño
El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), a naturally occurring climate pattern involving changes in ocean temperatures and the atmosphere over the central and eastern tropical Pacific. It typically occurs every two to seven years and can influence temperature and rainfall patterns across large parts of the world. (WMO, El Niño/La Niña)
El Niño is not itself a disaster or a single hazard. Rather, it changes the likelihood of conditions that can contribute to drought, flooding, extreme heat, wildfire and other hazards. Its effects vary considerably between regions and between individual events. (WMO, El Niño/La Niña; UNDRR, 2026)
This matters for disaster risk reduction because El Niño can be forecast months in advance. Seasonal forecasts provide time to assess how changing climate conditions may interact with exposure, vulnerability and existing risks, and to prepare before impacts occur.
Forecasts are probabilistic. They indicate that some conditions have become more or less likely – they do not predict exactly what will happen in a particular place. Climate information therefore needs to be combined with historical impacts, exposure, vulnerability and other risk information, and updated as forecasts and conditions evolve. (UNDRR and WMO, 2023)
El Niño shifts rainfall patterns in different parts of the world. Regional anomalies vary depending on the season.
Graphic: World Meteorological Organization.
Source: Lenssen, N. J. L., L. Goddard and S. Mason, 2020: Seasonal Forecast Skill of ENSO Teleconnection Maps. Weather and Forecasting, 35, 2387-2406, doi.org/10.1175/WAF-D-19-0235.1
The 2026-27 event in numbers
WMO August–October 2026 forecast
FAO, developing countries
WFP projection, August 2026
How El Niño can change risk
El Niño influences atmospheric circulation around the world, but its effects are not uniform. The same event can bring excess rainfall to one region and drought to another, and impacts may also vary considerably within countries.
El Niño is commonly associated with:
- increased rainfall in parts of southern South America, the southern United States, East Africa and central Asia;
- drier conditions in parts of Central America, northern South America, the Caribbean, Australia, Indonesia, southern Africa and South Asia; and
- changes in temperature and in the likelihood of climate extremes. (WMO, El Niño/La Niña)
These broad patterns are useful for understanding potential risk, but they should not be treated as local forecasts. National Meteorological and Hydrological Services, Regional Climate Centres and Regional Climate Outlook Forums provide more detailed and regularly updated information for particular countries and regions. (WMO)
The strength of an El Niño event is only one factor determining its impacts. Events also differ in their timing, duration and the location of ocean warming, and they interact with other climate drivers. A strong El Niño will therefore not necessarily reproduce the impacts of previous strong events.
Impacts may also cascade across sectors and national borders. Past El Niño events have affected agriculture and food systems, water supplies, energy, health, transport, fisheries and supply chains. In 1997–1998, for example, drought and fires in Indonesia generated widespread transboundary haze across South-East Asia, while low water levels have affected operations of the Panama Canal during major El Niño events.
El Niño and the components of risk
Risk is the product of hazard, exposure and vulnerability, reduced by the capacity to anticipate and cope. El Niño rises from beneath the equation. It amplifies the hazard term, and its impact feeds on the exposure and vulnerability already in place, which is why the same event causes far more harm in some places than in others. Because it is forecastable seasons ahead, it can also raise capacity through anticipatory action, which pulls risk back down. El Niño is a physical ocean-atmosphere phenomenon, not a product of exposure or vulnerability: the inward arrows show what its impact draws on, not what creates it. Hover any element, or click to open its reference page.
Shown for the warm phase (El Niño); the cold phase (La Niña) has a different, often opposite, hazard signature. El Niño typically drives several hazards at once, so the single hazard term simplifies a multi-hazard reality. Adapted from Components of risk on PreventionWeb, with capacity per UNDRR terminology.
From climate forecasts to risk information
Seasonal forecasts are most useful when they are translated into information about possible impacts.
An increased probability of below-average rainfall, for example, may have very different consequences depending on water storage, crop calendars, livelihood patterns, existing food insecurity or the condition of local ecosystems. Similarly, above-average rainfall may replenish reservoirs in one place while increasing flood and landslide risk in another.
Risk assessments can therefore combine seasonal forecasts with information on:
- previous disaster impacts;
- population and infrastructure exposure;
- poverty, food insecurity and displacement;
- water resources and agricultural conditions;
- ecosystem health;
- critical infrastructure and services; and
- institutional and response capacity.
This helps identify not only where a climate anomaly may occur, but where it is most likely to produce serious consequences and who may be most affected.
Different types of climate and weather information also support decisions at different stages. Seasonal forecasts can inform strategic planning, resource allocation and contingency financing several months ahead. Sub-seasonal forecasts can refine preparedness as conditions become clearer. Short-range forecasts and warnings support operational action as specific hazards approach.
El Niño forecasts are updated as ocean and atmospheric conditions evolve, and confidence can change considerably over the course of an event. Risk assessments and preparedness decisions should therefore be revisited regularly rather than based on a single seasonal outlook.
Risk assessment should therefore be iterative rather than based on a single forecast.
Guidance on using climate information for risk management
El Niño in a changing climate
El Niño is a feature of natural climate variability, but it now occurs against the background of a warmer climate.
There is not currently clear evidence that climate change is increasing the frequency of El Niño events themselves. However, higher background temperatures can intensify some associated impacts, including extreme heat, marine heatwaves and heavy rainfall. (WMO)
La Niña, the cool phase of ENSO, should not be understood simply as El Niño in reverse. It produces different patterns of climate variability and risk, and can follow an El Niño event. Risk monitoring and preparedness therefore need to continue through the transition between ENSO phases.
Anticipatory risk management
The lead time associated with El Niño creates opportunities to act before impacts occur.
Effective anticipatory risk management requires coordination because El Niño-related risks rarely affect one sector alone. Reduced rainfall, for example, may simultaneously affect agriculture, drinking water, hydropower and ecosystems. Excess rainfall can affect housing, transport, health services, agriculture and livelihoods.
Meteorological and hydrological services, disaster risk management authorities and ministries responsible for agriculture, water, health, energy, finance and social protection therefore need mechanisms to assess changing risks together and agree on action. Local authorities, humanitarian and development actors, financial institutions and affected communities may also need to be involved, depending on the context.
Intermediary institutions are particularly important in turning climate information into decisions. Agricultural extension services, water managers, health surveillance systems and local authorities can interpret broad climate forecasts in terms of the sectors and populations they serve.
Where possible, preparedness plans should define in advance the thresholds, triggers, responsibilities and financing arrangements that will allow action to begin as risk increases.
What acting early can look like
Depending on the risks identified, measures may include:
- adjusting reservoir operations and securing water supplies ahead of forecast drought;
- supporting farmers with appropriate seed, irrigation advice or changes to planting schedules;
- protecting livestock and preparing feed and water supplies;
- pre-positioning food, medical and emergency supplies;
- expanding cash transfers or other social protection mechanisms before livelihoods deteriorate;
- preparedness and raising awareness at the community level;
- maintaining drainage, roads, dams and other critical infrastructure;
- strengthening health and disease surveillance where changing climate conditions increase health risks; and
- activating contingency funds, forecast-based financing or other pre-arranged financial mechanisms.
Anticipatory action can also make use of favourable conditions. Increased rainfall may offer opportunities for water storage, groundwater recharge, agricultural production or ecosystem recovery in some areas. Identifying those opportunities can form part of the same planning process used to reduce adverse impacts.
One weather phenomenon, many hazards
There is no hazard information profile for El Niño, and that is deliberate. Hazard profiles describe hazards. El Niño is a recurring mode of climate variability that shifts the probability, intensity and timing of hazards that already exist. These are the areas where it shows up most in our Knowledge Base.
One caution runs through all of these. Not every drought, flood or fire in an El Niño year is caused by El Niño, and over-attribution is a common error. The climate signal shifts probabilities; what turns a shifted probability into a disaster is exposure and vulnerability.
What past events taught us
Impact is not determined by intensity alone. According to EM-DAT, the 1997-98 event is associated with more than 1,200 deaths in Latin America and the Caribbean, mostly from floods and landslides in the Andean countries. The 2014-16 event affected far more people worldwide, with humanitarian need reaching tens of millions, yet recorded far fewer deaths.
Better anticipation and wider early warning coverage were part of that difference. So was a different hazard mix: 1997-98 mortality was driven by rapid-onset floods and landslides, which kill quickly and are counted precisely, while 2015-16 impacts were dominated by slow-onset drought and food insecurity, where excess mortality is systematically under-recorded. The comparison is instructive, but it is not a clean experiment.
The 2023-24 event tested the same lesson again. Prolonged drought hit the Central American Dry Corridor, Bolivia and Colombia while the coasts of Ecuador and Peru flooded. In the Amazon, the Rio Negro at Manaus fell in October 2023 to its lowest level in more than a century of records, a record broken again the following year.
What happens if El Niño further disrupts the Panama Canal? Video: UNDRR
Kamal Kishore: Eleven lessons in risk governance from the Panama Canal →
UNDRR's position on El Niño
A shift in the Pacific Ocean that raises the odds of drought, flood, heat and fire across large parts of the world. Few risks come with this much warning, and whether that warning is used is as much a matter of governance as of meteorology.
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Search across PreventionWeb for El Niño and ENSO material. For the curated set, see the ENSO collection.
