The WMO said the climate phenomenon, which is already firmly established, is expected to become “very strong” and reach its peak around the end of the year. The probability of El Niño continuing through February 2027 is now close to 100%.
The unusually strong forecast comes amid exceptionally warm ocean temperatures. Scientists have recorded a large reservoir of unusually warm water beneath the surface of the tropical Pacific, with subsurface temperatures in some areas more than 8°C above average during July and early August.
UN Secretary-General António Guterres described the development as a “supersized” El Niño, warning that the planet is entering increasingly uncertain climate conditions.
El Niño is a naturally occurring climate pattern that typically develops every two to seven years when waters in the central and eastern equatorial Pacific become unusually warm. The warming can alter atmospheric circulation and influence rainfall and temperature patterns across distant parts of the world.
The current El Niño is developing against a backdrop of already exceptionally warm global oceans. While scientists have not established that human-caused climate change is making El Niño itself stronger, a warmer atmosphere and ocean can intensify some of its effects by increasing the heat and moisture available to fuel extreme weather.
The Niño 3.4 index, a key measure of sea surface temperatures in the central tropical Pacific, averaged 1.5°C above normal from May to July and reached 2°C in July. Weekly readings from late July through mid-August climbed as high as 2.6°C.
Forecasters expect above-average temperatures across almost the entire globe between September and November. Rainfall patterns are also expected to show the typical effects of El Niño, increasing the likelihood of heavy rain and flooding in some regions while raising drought risks in others.
The WMO noted that other climate patterns, including a positive phase of the Indian Ocean Dipole and unusually warm tropical Atlantic waters, could further influence regional weather conditions. As a result, the strength of El Niño alone cannot be used to predict the exact impacts on individual countries.
WMO Secretary-General Celeste Saulo said the strengthening El Niño could have significant consequences for communities and economies worldwide, particularly through worsening droughts and floods.
The World Health Organization has also launched an unprecedented mobilisation involving national weather agencies to strengthen forecasting and early-warning systems ahead of the expected impacts. The initiative aims to help governments and humanitarian organizations prepare for risks to agriculture, public health, energy and water supplies.
“This exceptional El Niño demands exceptional preparedness and response,” Saulo said.
With the phenomenon yet to reach its expected peak, forecasters are now focused on determining how intense it will become and the extent of the heat and weather disruption it could cause worldwide.