The reference index used to determine whether and when we enter an El Niño phase is called the ONI (Oceanic Niño Index). It is based on measurements of surface water temperatures in a specific area of the Pacific known as Niño 3.4. Specifically, the ONI represents the difference between the historical reference average temperature (1971–2000) and the three-month average temperature. When this anomaly is equal to or greater than +0.5°C for at least five consecutive three-month periods, the event is officially classified as El Niño.

A few weeks ago, the WMO (World Meteorological Organization) officially announced that the probability of the event reaching very strong intensity in the September–November 2026 period, and persisting into the following period, is close to 100% [1].
The reason so much attention is being paid to the developing El Niño is that, according to experts, it will be particularly intense. Forecasts estimate that in the coming months the ONI will exceed the +2°C threshold, above which the phenomenon reaches a higher level of intensity and is therefore defined as a Super El Niño.
Looking at historical data, such a high value as early as July had never been recorded before. If the WMO forecasts are confirmed, the incoming El Niño would therefore be the strongest ever recorded.

Figure 2: ONI (Oceanic Niño Index) trend, 2015 – 2026, calculated against the historical reference average (1971–2000).  Data from NOAA; analysis by Stefano Fisco, 2026. 

Starting with ocean warming, El Niño triggers a chain of climatic effects, including changes in the normal seasonality of winds and the distribution of rainfall. Some regions experience prolonged periods of drought, while others see rainfall intensify.

Although the direct effects on activities such as agriculture are easy to imagine, they are not the only ones. Changes in water temperatures along the coast of Peru alter marine ecosystems. During El Niño, rising surface temperatures and changing oceanographic conditions are unfavorable to the Pacific anchovy, a species of fish known as the Peruvian anchoveta. Global fishmeal production depends on this species, as fishmeal is used as feed in the farming of species such as salmon and shrimp.
Due to high temperatures in the western Pacific, the availability of Pacific anchovy declined by between 30% and 40% in a single year, resulting in higher prices for aquaculture products. The intensification of El Niño is expected to worsen this shortage further [2].

The energy sector is among those most exposed to the consequences of phenomena such as El Niño, particularly in Latin American and Caribbean countries. In this region, according to IEA data, hydropower accounts for 53% of electricity generation, with shares reaching 90% in Venezuela and as high as 100% in Paraguay. Such dependence makes electricity systems particularly sensitive to changes in water availability caused by periods of drought. To compensate for the shortfall in hydropower generation, electricity systems turn to thermal power plants, while simultaneously increasing their exposure to fossil fuel prices and emissions.
A 2025 study by the IDB (Inter-American Development Bank), focusing on Chile’s electricity system, confirmed that during periods of drought, emissions associated with electricity generation can increase by up to 34% [3].

As the alert level intensifies, governments and international organizations are beginning to take action.
The WMO, together with the UN, has established the Early Warnings for All initiative, with the aim of making real-time weather monitoring systems available, particularly to the most vulnerable countries, so that governments can take anticipatory action to prevent disasters.
FAO and WFP are supporting programs to plant crops that are resistant to drought and flooding, while increasing food reserves and water-storage systems in countries at risk of drought [4].
Brazil and Colombia are taking steps to implement forest-fire prevention plans. Ecuador is investing in flood and landslide prevention; Costa Rica is diversifying its renewable energy mix beyond hydropower. Panama is developing operational plans for managing the canal in the event of low water levels [5].

The maximum alert issued by the WMO is now possible largely thanks to advances in climate monitoring systems, which make it possible to build highly accurate forecasting models for El Niño. However, knowing in advance is not enough to prevent the consequences of extreme climate events. What is needed is a commitment from the governments of the countries most exposed. In these countries, a strong El Niño means electricity rationing and energy prices that can multiply. It also means coastal communities losing their main source of income, as in the case of anchovy fishing.
The incoming Super El Niño is also a testing ground for the challenges that climate change will pose in the coming years. It is an opportunity to understand whether the forecasting capabilities we have achieved have truly been translated into concrete action.

Cover and preview photo: Abandoned canoes on a lake bench. Photo by YODA Adaman on Unsplash.