El Nino is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean with on average five year intervals. It is characterized by variations in the temperature of the surface of the tropical eastern Pacific Ocean - warming or cooling known as El Nino and La Nina respectively - and air surface pressure in the tropical western Pacific - the Southern Oscillation. The two variations are coupled: the warm oceanic phase, El Nino, accompanies high air surface pressure in the western Pacific, while the cold phase, La Nina, accompanies low air surface pressure in the western Pacific. Mechanisms that cause the oscillation remain under study. Read more ...
A super El Nino winter is coming and the first official forecast is in CNN - October 15, 2026
The central Pacific Ocean just broke a temperature record above 86°F. Experts say it might signal a new kind of El Nino. Live Science - October 9, 2026
El Nino forecast to become very strong by late 2026, raising extreme weather risks into 2027 Watchers - September 3, 2026
The probability of a very strong El Nino during October-December rose from 81% in CPC's July assessment to 95% in August Watchers - August 18, 2026
The El Nino weather pattern picked up strength over the past month and is highly likely to "rank among the largest" ever recorded when it peaks between October and December PhysOrg - July 8, 2026
A Super El Nino is coming: 5 hard-won lessons the world can learn from Africa PhysOrg - July 7, 2026
This year's El Nino likely to become record-breaker: Top expert PhysOrg - July 7, 2026
El Nino and La Nina are officially defined as sustained sea surface temperature anomalies of magnitude greater than 0.5°C across the central tropical Pacific Ocean. El Nino is associated with a positive anomaly, and La Nina with a negative anomaly. When the condition is met for a period of less than five months, it is classified as El Nino or La Nina conditions; if the anomaly persists for five months or longer, it is classified as an El Nino or La Nina episode. Historically, it has occurred at irregular intervals of 2-7 years and has usually lasted one or two years.
La Nina is a coupled ocean-atmosphere phenomenon that is the counterpart of El Nino as part of the broader El Nino-Southern Oscillation climate pattern. During a period of La Nina, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3-5 °C. In the United States, an episode of La Nina is defined as a period of at least 5 months of La Nina conditions. The name La Nina originates from Spanish, meaning "the little girl," analogous to El Nino meaning "the little boy."
La Nina, sometimes informally called "anti-El Nino", is the opposite of El Nino, where the latter corresponds instead to a higher sea surface temperature by a deviation of at least 0.5 °C, and its effects are often the reverse of those of El Nino. El Nino is known for its potentially catastrophic impact on the weather along the Chilean, Peruvian, New Zealand, and Australian coasts, among others. It has extensive effects on the weather in North America, even affecting the Atlantic Hurricane Season. La Nina often, though not always, follows an El Nino.