What are El Niño and La Niña?
Plainly said, they are meteorological events that occur roughly every two to seven years on average (but have no regular schedule) in the Pacific ocean and typically last anywhere from 9 to 12 months.
In scientific terminology, they are a part of the so-called El Niño-Southern Osciallation (ENSO) climate pattern, arguably the most influential climate driven pattern on planet Earth,
Its cycles of warm and cool waters in the central and eastern equatorial Pacific alter where ocean heat is released into the atmosphere, influencing atmospheric circulation, temperatures, precipitation and other weather events that affect agriculture, wildfires and marine fisheries around the globe.
Climate records of El Niño go back millions of years, with evidence of the cycle found in ice cores, deep sea muds, coral, caves and tree rings.
What drives them?
The main factors are the interaction between trade winds strength, ocean temperatures and shifts in the Pacific jet stream.
To begin understanding these terms, we should clarify what each one of these is.
- Trade winds blow east to west just north and south of the equator, and are relatively close to Earth’s surface. Sailors traveling from Europe or Africa used the trade winds to travel to North or South America. These trade winds can also steer storms and hurricanes.
- Jet streams are bands of strong wind that generally blow from west to east all across the globe at a higher altitude, in the troposphere [which begins at Earth’s surface and is around 18-20km (11-12 miles) high at the Equator].
Much like the trade winds, jet streams can be beneficial to travel, more specifically in shortening airplane travel from west to east as the area of the atmosphere where jet streams take place is the same as where airplanes operate.
This is why a flight from Los Angeles to New York last less (typically around 5 to 5 1/2 hours) than a flight from New York to Los Angeles (average flight time varies between 6 to 6 1/2 hours).
Having cleared that out, we can begin to get into the specifics of El Niño and La Niña.
What are the normal conditions in the Pacific ocean?
During normal conditions in the Pacific, trade winds blow west along the equator, taking warm water from the ocean’s surface near South America towards Asia.
To replace that warm water, cold water rises from the depths of the ocean – this is a process called upwelling.
When El Niño and La Niña occur, these normal conditions are broken.
So what happens when El Niño occurs?
The term was first coined by Spanish firshermen in the 17th century, who noticed that there are extended periods of warm water in the Ocean around December. El Niño means little boy in Spanish, and in reality the full term is El Niño da Navidad (because of the occurrence of the event in the month of December, when Christmas is celebrated).
During El Nino, ocean water temperature rises, trade winds weaken, which causes the Pacific jet stream to move south of its neutral position.
For El Niño conditions to form, monthly sea surface temperatures in the central and eastern tropical Pacific Ocean (Nino 3.4 region) need to warm +0.5° Celsius above normal, persisting for at least five consecutive overlapping three-month periods.
In addition, the atmosphere must respond to the warming water by weakening the prevailing winds, known as the trade winds, and also shift patterns of tropical rainfall eastward.
This ocean–atmosphere coupling impacts the position of the Pacific jet stream and influences weather and climate patterns globally.
EL Niña, El Viejo, Anti-El Niño
During La Niña (Little Girl in Spanish) events, trade winds grow stronger, pushing more warm water towards Asia. In turn, to replace that warm water, the upwelling brings more cold water from the ocean’s depths to the surface.
The colder than usual water of course pushes the Pacific jet stream north-ward. This leads to drought conditions in the southern U.S and heavy rains and flooding in the Pacific Northwest and Canada.
Impacts on U.S. and Global Weather
The influence of El Niño varies by region and season.
Its effects are most pronounced in the Northern Hemisphere, particularly the United States, during the winter months. Conversely, tropical latitudes see the greatest impact during the summer and fall, coinciding with the peak of hurricane season in September and October. As the event matures, the influence of ENSO on Atlantic hurricanes generally becomes more evident during the latter portion of the hurricane season, specifically from September through November.
El Niño often brings above-average winter temperatures to Alaska, the Pacific Northwest and northern U.S., while California, the Southwest and Gulf Coast typically experience cooler conditions and more frequent rainstorms.
This can increase flooding, mountain snowfall and landslide risk across the southern states. It also suppresses Atlantic hurricanes by increasing wind shear but favors more tropical cyclones in the eastern Pacific. Globally,
El Niño can produce extreme heat and drought in Australia, Indonesia, southern Africa and parts of India, while Peru, Ecuador and East Africa may receive unusually heavy rainfall and flooding.
La Niña generally brings colder, wetter and snowier winters to the Pacific Northwest and northern Rockies, while the southern U.S. often experiences above-average temperatures, reduced rainfall, drought and increased wildfire risk. It also a great predictor of a stronger Atlantic hurricane season.
Elsewhere, La Niña often brings heavier monsoon rainfall to Australia and Southeast Asia, wetter conditions in southern Africa, and drought across parts of South America and East Africa. Bear in mind that these are typical patterns, not guaranteed outcomes.
How are these climate patterns detected and predicted?
The National Oceaninc and Atmospheric Association ( NOAA) is the primary body that tracks and predicts these climate patterns,
NOAA classifies El Niño events as weak, moderate, strong or very strong. Each event develops differently, so its weather effects can vary from one occurrence to another.
NOAA’s National Weather Service monitors El Niño using information from satellites, anchored and drifting buoys, ships and sea-level measurements. These observations are processed through computer models to help forecasters assess current conditions and future changes. A team of 10 specialists reviews the results and publishes a consensus forecast on the second Thursday of every month.
Predicting when El Niño will begin is challenging because several changes in the Pacific Ocean and atmosphere must occur together. Once the event is established, however, forecasters can usually estimate its strength and development with greater confidence.
Sea-surface temperatures across the equatorial Pacific are among the most important indicators. Forecasters also examine whether the warming water is affecting the atmosphere, particularly whether the tropical trade winds are weakening or reversing toward South America. This interaction between the ocean and atmosphere is essential for an El Niño event to develop.
After the powerful 1982–1983 El Niño exposed the need for real-time Pacific Ocean data, NOAA developed the Tropical Atmosphere Ocean Array. The network includes about 70 anchored buoys across the equatorial Pacific that measure winds, air pressure, air temperature and near-surface water temperature. Data are transmitted by satellite to forecasters, researchers and sectors including agriculture, fisheries, public health and water management.
Since 2014, NOAA and the Japan Agency for Marine-Earth Science and Technology have worked with international partners to modernize this system. The broader Tropical Pacific Observing System combines TAO measurements with information from satellites, drifting instruments and Argo floats, providing a more complete picture of changing ocean and atmospheric conditions.
On February 1, 2026, NOAA began operational use of the Relative Oceanic Niño Index. Unlike the traditional index, RONI accounts for overall tropical ocean warming, helping scientists identify El Niño and La Niña more consistently in both historical records and real-time forecasts.
NOAA also studies how ENSO affects drought, wildfires, flooding and food security worldwide. Historical data and climate models help researchers distinguish between different El Niño events and anticipate how their effects may change in the coming decades.
Their effect on Hurricanes and Tornadoes
El Niño and La Niña have opposite effects on hurricane activity in the Atlantic and Pacific. El Niño generally favors more hurricanes in the central and eastern Pacific while suppressing activity in the Atlantic. La Niña usually reduces Pacific activity but supports more Atlantic storms.
The main driver is vertical wind shear, which is the change in wind speed and direction between the lower and upper atmosphere. Strong shear can prevent tropical storms from organizing or tear developing hurricanes apart.
La Niña reverses this pattern. Wind shear strengthens over the Pacific, suppressing hurricanes, while weaker upper-level winds over the Caribbean and tropical Atlantic reduce shear and allow storms to organize more easily. La Niña also decreases atmospheric stability and sinking motion across the Atlantic.
ENSO is not the only influence on hurricane seasons. Longer-term Atlantic and Pacific temperature patterns, ocean warmth, the West African monsoon and atmospheric moisture also play important roles. As a result, El Niño or La Niña does not determine a season alone. Its effects depend on how it interacts with these wider climate conditions.
When will the next El Nino occur?
NOAA monitors the ENSO patterns thoughout the year continuously, on a monthly ( on the second Thursday of every month) basis, including in periods when neither El Niño nor La Niña is active.
When development is possible, NOAA may issue an El Niño Watch or La Niña Watch. Once conditions have developed and are expected to continue, it issues an Advisory.
As of the publication of this article (August 5th, 2026) the last brief took place on July 9th, 2026.
In it, a El Niño advisory was issued, stating that the pattern continues and will strengthen through the end of the year, with a 97% chance it will persist through early spring 2027.
Sea-surface temperatures rose more than 1°C (1.8°F) above average across much of the central and eastern equatorial Pacific. Models indicate it will intensify through late 2026, with a 97% chance of lasting into early spring 2027.
There is an 81% chance of a very strong El Niño from October to December.
NOAA’s next update is due August 13, 2026.
