The most recent El Nino, in 2023 to 2024, contributed to 2024 being the hottest year on record, Saulo added.
A shift has been observed in the Equatorial Pacific, with sea surface temperatures rising rapidly from late April to mid-May, suggesting El Nino conditions were developing, the WMO said.
The agency also said that it has observed unusually warm subsurface conditions across the tropical Pacific with temperatures exceeding 6°C above average, creating a reservoir of heat that is driving surface warming.
The weather pattern is known to disrupt regional climates, potentially bringing increased rainfall to southern South America, the southern United States, parts of the Horn of Africa and central Asia, while causing drought in Australia, central America, Indonesia and sections of southern Asia.
It can also have a warming effect on the global climate and fuel hurricanes in the central and eastern Pacific Ocean, the WMO said.
“The world must treat it as the urgent climate warning it is. El Nino conditions will pour fuel on the fire of a warming world,” said UN Secretary-General António Guterres, urging a shift away from fossil fuels towards renewable energy.
While there is no evidence that climate change increases the frequency or intensity of El Nino events, it can make associated impacts such as extreme heatwaves and heavy rainfall worse, according to the WMO.