What are El Niño and La Niña?
The following overview comes from an article on the World Meteorological Organization (WMO) website, where you can find more information.
El Niño and La Niña are opposite phases of a naturally occurring climate pattern known as the El Niño-Southern Oscillation (ENSO), involving fluctuating ocean temperatures in the central and eastern equatorial Pacific, coupled with changes in the overlying atmosphere.
ENSO has two opposite extreme phases: the warm phase, known as El Niño, and the cold phase, known as La Niña. Between these extremes lies a third state called ENSO-neutral. El Niño can typically last up to 18 months and La Niña up to three years.
El Niño is characterized by unusually warm ocean surface temperatures in the central and eastern Pacific. The name originates with Peruvian fishermen and sailors who noticed a warm current, associated with reduced fish catches, and named it El Niño (“the Christ Child”), likely because it typically became noticeable around Christmas . In contrast, a La Niña event is characterized by unusually cool ocean surface temperatures in the same region and an intensification of the prevailing east to west surface winds.
In the Pacific Ocean, warmer-than-normal ocean temperatures usually mean El Niño conditions, which happen when easterly trade winds become weaker. Cooler-than-normal temperatures usually mean La Niña conditions, when easterly winds become stronger. During the Neutral phase, ocean temperatures in the tropical Pacific stay close to normal.
The transition between these extreme phases typically occurs every two to seven years. Both El Niño and La Niña generally begin developing between March and June and reach their peak intensity between November and February.
The effects of each El Niño/La Niña event vary depending on the intensity, duration, time of year when it develops, and how it interacts with other climate variability modes (such as the Indian Ocean Dipole). Not all regions of the world are affected, and even within a region, impacts can be different. Even when ENSO is neutral, extreme weather can still occur.
The strength of an ENSO event is highly significant – whether it is classed as weak, moderate, strong or very strong. WMO does not use the term Super El Niño or La Niña.
Improved seasonal forecast models can now predict climate patterns one to six months in advance. By identifying trends in heavy rainfall (potentially leading to floods) and drought conditions, this information provides early warning signals that support planning in climate-sensitive sectors such as agriculture and health, while also informing the activation of government emergency protocols and the pre-positioning of humanitarian supplies Together, these actions help to protect resources and save hundreds of millions of dollars and many thousands of lives.
A multiyear La Niña lasted from late 2020 to early 2023, followed by the strong El Niño of 2023–2024. ENSO-neutral conditions began in April–June 2024 and generally prevailed until September–November 2025, with a brief dip into weak La Niña conditions during late 2024 and early 2025. La Niña developed again in late 2025 and lasted until early 2026.
WMO’s Global Seasonal Climate Update issued in May 2026 signals a clear shift in the Equatorial Pacific: sea-surface temperatures are rising rapidly, pointing to a likely return of El Niño conditions as early as June–July–August 2026. Forecasts indicate there is a “nearly global dominance of above-normal land surface temperatures” in the upcoming three-month period, and regional variations in rainfall patterns.