GENEVA — El Nino, a powerful climate pattern that warms the tropical Pacific Ocean and disrupts weather around the world, could reach unprecedented strength by December, United Nations officials warned Wednesday, urging governments to prepare for extreme heat, droughts and flooding that could threaten millions of people into 2027 and beyond.

The World Meteorological Organization forecast that sea surface temperatures in the tropical Pacific could reach 3.8 degrees Celsius (6.8 degrees Fahrenheit) above average during November through January. If realized, the reading would exceed previous records for the three-month period, raising concerns about severe disruptions to rainfall, agriculture and water supplies.

Celeste Saulo, secretary-general of the WMO, said the developing event could exceed the monitoring range used by the agency over the past four decades. She warned that extreme weather events already affecting some regions could intensify as the climate pattern strengthens.

The warning came as the WMO and the U.N. humanitarian office called for immediate, coordinated preparations to protect vulnerable communities. Tom Fletcher, the U.N. undersecretary-general for humanitarian affairs, said as many as 50 million people could face increased hunger as weather extremes compound conflict, displacement, high food prices and cuts to humanitarian assistance.

What Is El Nino?

El Nino is a naturally occurring climate phenomenon characterized by unusually warm surface waters in the central and eastern equatorial Pacific Ocean. It is part of the El Nino-Southern Oscillation, a recurring pattern involving interactions between ocean temperatures, atmospheric pressure and winds.

Under normal conditions, trade winds blow from east to west across the tropical Pacific, helping push warm surface water toward Asia and Australia. During El Nino, those winds weaken, allowing warmer water to spread eastward toward the Americas.

The shift changes where heat and moisture enter the atmosphere, influencing wind patterns, storm tracks and the distribution of rainfall across the globe.

El Nino events generally occur every two to seven years and typically last nine to 12 months, although their timing, strength and effects vary. The opposite phase, La Nina, features cooler-than-average surface waters in the central and eastern tropical Pacific. Periods between the two phases are considered neutral.

El Nino is not itself a storm, hurricane or single weather event. It is a large-scale climate pattern that changes the likelihood of certain weather conditions in different regions.

Drought in Some Regions, Floods in Others

The effects of El Nino are not uniform. Some areas experience prolonged dry conditions, while others face unusually heavy rainfall, flooding and increased storm risks.

Parts of Central America and the Amazon region can face heightened drought risk, threatening crops, livestock and water supplies. In eastern and southern Africa, changing rainfall patterns can worsen food insecurity in communities already struggling with conflict, displacement and limited access to assistance.

Other areas of the Americas may experience heavier rainfall. Parts of western South America, including areas of Chile and the broader Parana basin, have faced flooding concerns as regional weather patterns shift.

Across Asia and the Pacific, El Nino can increase the risk of drought and heat in some locations, while other places remain vulnerable to intense rainfall, flooding and tropical cyclones. The specific impacts depend on local conditions and the timing of seasonal weather systems.

Scientists caution that El Nino does not determine every storm or drought. Regional forecasts are needed to identify where the risks are greatest and how conditions may develop over time.

Climate Change Can Intensify the Heat

El Nino naturally raises global temperatures by releasing additional heat from the tropical Pacific into the atmosphere. When it occurs against the backdrop of human-caused climate change, the warming effects can compound the long-term rise in global temperatures.

The previous major El Nino helped make 2023 one of the hottest years on record and contributed to the record global temperatures measured in 2024. Greenhouse gas emissions remain the primary driver of long-term global warming, while El Nino can add a temporary boost to average temperatures.

A strong event can also affect agriculture, fisheries and ecosystems. Warmer ocean waters alter the distribution of marine species, while droughts and floods can reduce crop yields, damage infrastructure and disrupt food supply chains.

The potential consequences extend beyond the regions experiencing the most severe weather. Agricultural losses can push food prices higher, damage to transport networks can interrupt trade, and shortages of water or basic supplies can increase pressure on already fragile communities.

U.N. Urges Countries to Prepare Before Disaster Strikes

Fletcher described El Nino as a major threat to regions already affected by humanitarian emergencies. He urged governments, development banks and international financial institutions to release funding before extreme weather makes it more difficult to deliver aid.

The U.N. humanitarian office said it had released $50 million to support preparedness in 11 countries, including Chad, El Salvador, Ethiopia, Somalia and South Sudan.

Preparation priorities vary by region. In parts of the Horn of Africa, humanitarian agencies may need to position food, water and emergency supplies ahead of heavy rains. In southern Africa, farmers may need seeds and livestock support to recover from drought. Central American communities may require help protecting livelihoods, while parts of Asia and the Pacific need plans for drought, flooding and cyclones.

Early-warning systems, emergency supplies, drought-resistant farming practices and well-coordinated evacuation plans can reduce the effects of extreme weather. Forecasts are most useful when governments and aid organizations have the resources to act on them.

Saulo emphasized that the climate phenomenon cannot be stopped, but its worst consequences can be reduced through preparation.

What El Nino Could Mean for the US

El Nino can influence U.S. weather by shifting the position of the jet stream, a high-altitude band of winds that helps steer storm systems.

During winter, the pattern often increases the likelihood of wetter conditions across parts of the southern United States, from California through the Gulf Coast and toward the Southeast. The northern tier of the country can be more likely to experience warmer-than-average conditions.

These are seasonal tendencies, not guarantees. Local temperatures, precipitation and individual storms depend on other atmospheric conditions as well, and the strength of an El Nino event can affect the odds of particular outcomes.

The National Oceanic and Atmospheric Administration has said the developing event is likely to influence the winter outlook for December 2026 through February 2027, with above-average temperatures favored in parts of the northern United States and wetter conditions favored across parts of the South and East.

Residents should follow forecasts from the National Weather Service and local emergency management officials rather than assume that every region will experience the same effects.

Preparedness Will Determine the Human Cost

The growing El Nino threat underscores the importance of translating climate forecasts into practical action. Governments can prepare emergency shelters, strengthen flood defenses, protect water supplies and help farmers adjust planting decisions before conditions deteriorate.

For households, preparedness may include following local weather alerts, keeping emergency supplies available, understanding evacuation routes and taking drought or flood guidance seriously.

Scientists will continue monitoring Pacific Ocean temperatures and atmospheric conditions as the event develops. Although the forecast points to an exceptionally strong El Nino, its precise regional effects remain uncertain.

The central warning from U.N. officials is that extreme weather does not automatically have to become a humanitarian catastrophe. Timely funding, reliable forecasts and early action can help protect lives and livelihoods as the climate pattern approaches its expected peak.

Editorial note: The WMO's 3.8-degree figure refers to the forecast anomaly in tropical Pacific sea surface temperatures, not a projected increase in global air temperature. The strength and regional effects remain subject to forecast updates.