Fuelled by exceptionally warm Pacific waters, the El Niño climate pattern is intensifying and has yet to peak. Forecasters are almost certain it will persist through February 2027 - with unusually warm conditions expected across much of the world in the coming months.
El Niño is strengthening rapidly in the Pacific Ocean, raising the prospect of months of extreme heat, floods, drought, and disruptive weather around the globe.
The phenomenon, already firmly established, is expected to become "very strong" and peak around the end of the year, according to new forecasts from the World Meteorological Organization (WMO) .
The likelihood that El Niño will persist through February 2027 is now close to 100 per cent. Never before has the UN weather agency issued such an unequivocal forecast for El Niño or its cooler counterpart, La Niña .
A supersize problem
And beneath the surface of the tropical Pacific lies another cause for concern. An enormous reservoir of unusually warm water that could continue feeding El Niño in the months ahead.
In some parts of the Pacific, subsurface temperatures in July and early August were more than eight degrees Celsius (around 14 degrees Fahrenheit) above normal.
The combination points toward an unusually powerful climate event unfolding on a planet already significantly warmer because of greenhouse gas emissions.
"El Niño is being supersized before our eyes," UN Secretary-General António Guterres said in a press release on Thursday. "The science leaves no room for doubt: the planet is in uncharted waters, and those waters are heating up."
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. That warming can alter atmospheric circulation thousands of miles away, shifting rainfall and temperature patterns everywhere.
But this El Niño is developing against an unusual backdrop. The oceans are already exceptionally warm, providing a hotter baseline on which the natural climate cycle is playing out.
Scientists have not established that man-made climate change is increasing or intensifying El Niño. But a warmer atmosphere and ocean can amplify some of its consequences, increasing the heat and moisture available to fuel extreme weather.
The latest measurements show how quickly the current event is developing.
The Niño 3.4 index , a closely watched measure of ocean temperatures in the central tropical Pacific, averaged 1.5°C above normal from May through July. By July, it had reached 2°C, and weekly readings from late July through mid-August climbed as high as 2.6 degrees.
The heat extends well below the surface - a sign that the warming is not fleeting and that El Niño has considerable fuel left.
A global pattern, uneven consequences
A very strong El Niño does not mean that every region will experience disasters of the same magnitude.
From September through November, however, forecasters expect above-normal temperatures across nearly the entire Earth's surface.
Rainfall patterns are also taking on the characteristic signature of El Niño, with greater chances of heavy rain and flooding in some places and drought in others.
Other forces could complicate that picture. A positive phase of the Indian Ocean Dipole - another large-scale shift in ocean temperatures - is expected to develop, while the tropical Atlantic is forecast to remain unusually warm.
Those overlapping patterns make it impossible to translate the strength of El Niño into a precise forecast for any individual country. But collectively, the signals point toward a period of heightened risk.
"El Niño means 'little boy' in Spanish, but it has the potential to deliver a massive blow to communities and economies around the world," Celeste Saulo, head of WMO , said. "We are already seeing the disruption and devastation caused by droughts and floods, and we expect these impacts to worsen as El Niño intensifies."
Historic mobilisation
The forecast has prompted an unusual response. It's the first time ever WHO has launched a mobilisation of this scale with national weather agencies, seeking to strengthen forecasts and early-warning systems as the risks mount.
The effort is intended to help governments and humanitarian organizations prepare for the effects on particularly vulnerable sectors, including agriculture, public health, energy and water supplies.
"This exceptional El Niño demands exceptional preparedness and response," Ms. Saulo said.
That underscores how much of this El Niño still lies ahead. The phenomenon is already exceptionally strong, and it has yet to peak.
The question is no longer whether El Niño will strengthen, but how much heat - and disruption - it will leave behind.
