El Nino will intensify before peaking in December and is nearly 100 per cent certain to last until February 2027, the World Meteorological Organisation says.
The forecast was outlined in its monthly Global Seasonal Climate Update on Thursday.
It said the weather event, which has been dubbed a 'Godzilla' El Nino in Indonesia, is likely to bring above-average temperatures and shift rainfall patterns, increasing the risk of drought and floods in regions across the globe.
“El Nino is firmly established and strengthening rapidly. WMO forecasts indicate a near-100 per cent likelihood that (El Nino) will persist through February 2027, potentially being one of the strongest since at least 1950," WMO Secretary General Celeste Saulo said in a statement released with the bulletin.
The UN weather body said sea surface temperatures in the central and eastern tropical Pacific, the region at the heart of the El Nino phenomenon, were expected to reach a record 3.7 degrees Celsius (6.7 degrees Fahrenheit) above normal from October to December.
The forecast temperature anomaly is significantly higher than the previous record of 2.6C from November 2015 to January 2016, it said.
“El Nino doesn't add new heat to the planet. It releases heat the ocean has already been storing beneath the surface - which is why a strong event so often becomes one of the hottest years measured (as with 2024),” Saulo told the Global Heat Forum in Bangkok.
“The ocean it's drawing from is the warmest we've ever measured it. There is simply more heat available to release,”
El Nino is the warm phase of the naturally occurring El Nino-Southern Oscillation cycle, a climate pattern that influences weather around the world.
It tends to cause higher global temperatures and disrupt rainfall patterns across large regions, meaning drought in some areas and heavy rains in others and typically occurs every two to seven years.
Mean global temperatures in August reached 16.96C, tying with July 2023 as the hottest month on record, according to the European Union's Copernicus Climate Change Service.
Researchers at the University of Chicago's Climate Impact Lab predicted last month that this year's "super-El Nino" was likely to result in as many as 451,000 excess deaths across the globe from June to February 2027.
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