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What is El Niño? Is it a storm?
ENSO El Niño, a natural cycle of warming of the ocean along the equator, can be monitored daily using satellites and buoys (image from July 27, 2026). El Niño is the warming of the water along the equator and NOT precipitation, a series of storms, or a jet stream. The warmer water can add energy to the atmosphere and enhance the existing weather patterns and jet streams, but where these storms move to is highly uncertain from month to month during the cool season. The same energy can support stronger tropical cyclones in the Pacific Ocean during the warm season.
Ocean
El Niño is warming of the ocean along the equator and is normal but a very strong El Niño is rare. The warmer water adds more energy in the form of wind and moisture. Therefore, the difference between cold air and warm moist air becomes greater (stronger jet stream wind).
Atmosphere
The atmosphere produces storms and precipitation which is normal. The atmosphere can be energized, or disrupted and the storm track altered when the tropical ocean warms or cools (e.g., El Niño and La Niña).
Results
The influences of El Niño are most impactful in the winter or cool season since the normal jet stream is normally much stronger and further south placing it across the US from November to April. El Nino influence does not create more storms, nor stronger, but can result in a more consildated persistent storm track leading to excessive precipitation in some regions and drier (less precipitation) in other areass of world. The exact path or region is not known far in advance and is not the same for each El Niño.
El Niño prediction is the easy part
El Niño is quite predictable far in advance but its impacts are not.
Model prediction of ENSO or equatorial sea surface temperatures.
These prediction plume charts are updated monthly.
ENSO El Niño is normal and occurs every 3 to 5 years. A strong El Niño ocean condition is predicted for 2026-2027, which creates unusually warmer water along the equatorial Pacific. El Niño is not a storm or excessive precipitation pattern, however, given El Niño and a normal winter jet stream (100-300 mile wide corridor), combined can enhance the storm track leading to more active weather anywhere for a portion of the 1,400 mile long West Coast. It can also reduce tropical cyclone activity in the Atlantic while increasing hurricanes in the Pacific.
El Nino
A prediction of the formaton of El Niño can be accurate as far as 1 year in advance such as 2015-16. The prediction is not precipitation but rather sea surface temperatures along the equator.
Atmosphere
How the atmosphere responds and where the storm track prevails (where storms travel) is usually not predictable more than 2-3 weeks in advance, since individual storms have not yet formed and the storm track is affected by more than El Niño influences.
Precipitation
We can use a combination of dynamic weather models and historical analog years along with climatology to help predict where precipitation and temperature will most likely be affected (departing from averages). However, each El Niño period has resulted in different outcomes of precipitation and temperature. Confidence was very high in 2015 but the strong El Niño and that winter (water year) resulted in below average precipitation for much of California, yet California and the West Coast have a stronger historical relationship to El Niño than most of the US.
El Niño and California precipitation
Looking at history
This table displays the top (wettest) California statewide precipitation by winter season. The average total is derived by including all climate zones (mountains, deserts, coast and valleys). The period from November to April is used since it is the core of the rainy season or active jet stream. The season total is compared against a 30 year average (1990 to 2020). While the wettest years on record were El Nino espisodes there are also La Nina years such as 2016-17 that produced excessive precipitation. This is not a measure of individual storms or atmospheric rivers. El Niño, Neutral and La Niña oceanic conditions can produce any type of storm cycle. The very strong El Niño of 2015-16 was ranked 46th wettest, only slightly above average.
El Niño analogs and precipitation - El Niño is not the weather
Why can't we use an analog (past history) and know what to expect with a given strength of El Niño conditions? While this appeared to have been an effective predictor for the 1997-98 El Niño (understanding 1982-83), the global ocean and atmospheric conditions are not the same in 2026, largely having observed significant warming (e.g., marine heat waves and record land temperatures) since 2000. This map depicts all ENSO El Niño winters that were ranked strong and very strong, compared to the most recent 30 year averages. The green and blue shaded basins indicate these regions were wetter than average and the yellow and orange were drier than average. However, individual seasons such as 2015-16 super El Nino were drier than average in the same green and blue shaded areas such as California. but very wet for Pacific Northwest, meanwhile 2016-17 and 2022-23 were equally or even wetter in California than the average El Niño season. El Niño is NOT precipitation and is not an atmospheric weather pattern but rather a sea surface temperature condition along the Equator. Therefore, the analog or historical comparison is only a simplified approach to the prediction of the storm track and the tangible weather impacts associated with precipitation and temperature.
Strong El Nino and Winter Outlook
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