The UN's secretary general, António Guterres, has warned the world to prepare.
"El Niño conditions will pour fuel on the fire of a warming world. Impacts will hit even harder, travel even farther, and cross borders with devastating speed," he said.
Droughts in parts of South America and South East Asia could hit crops at a time when the effective closure of the Strait of Hormuz is already disrupting the distribution of fertiliser. This could mean smaller harvests, reduced food supply and higher prices.
For fishing communities in South America, there is the risk of smaller catches. During El Niño, less cold, nutrient rich water comes to the surface, reducing food availability for marine species such as anchovies.
Some scientists are drawing comparisons with the 2015-16 El Niño, one of the strongest ever recorded.
At that time there were water shortages in the Caribbean, a record-breaking storm season in the central Pacific, and drought in the Horn of Africa.
The combination of storm events and widespread drought - at least partly the result of El Niño - led to food shortages affecting millions of people around the world, according to the UN's Food and Agricultural Organization.
