The onset was declared on 4 July 2023 by the World Meteorological Organization (WMO)[1][2][3][4] It was estimated that the most significant meteorological effects would occur between November 2023 and April 2024[5] and their characteristics would be determined depending on each territory on the planet,[6] within which droughts, heavy rains, wildfires, heat waves, tropical cyclones, flooding and changes in wind patterns occurred.

[1][7][8] These events have already negatively affected the economic activities of agriculture and fishing, generating shortages and rising prices of food—especially rice, palm oil, sugar cane, soybeans and corn—and, therefore, an increase in food insecurity of the most vulnerable populations.

[9] During an El Niño event, the east–west trade winds die, generating warmer air temperatures in the eastern and central parts of the tropical Pacific.

[7][13] The combination of El Niño and above-normal temperatures in the Atlantic Main Development Region (MDR) tends to favor increased hurricane activity in the eastern Pacific.

[14] At the beginning of the year, it was considered that the climatic conditions of the first quarter of 2023 pointed to the occurrence of a strong El Niño event, similar to those that occurred in 1982, 1997, and 2015.

[17][18][19] Given that Earth's average temperature has already increased by 1.2 °C since pre-industrial times, a large enough El Niño event in 2023-2024 could even push the planet, temporarily, into warming greater than 1.5 °C.

[30][31][32] The North West Pacific on the other hand observed well below average activity, mostly due to a consistently negative PDO environment, which suppressed the formation of a lot of tropical storms.

[34][35] World Meteorological Organization analyses indicated extreme heat and heatwave effects in central South America from August to December.

[37] The 2024 Rio Grande do Sul floods in May of that year were caused by historical heavy rains and storms in the southern Brazilian state.

This decision would affect more than 42 countries importing rice from India, especially Bangladesh, Nepal, Benin, Senegal, Ivory Coast, Togo and Guinea.

In India, the impacts of El Niño develop in such a way that precipitation is suppressed in almost the entire country, except in the territories located in the east and northeast.