El Niño is a phase of the natural climate cycle called ENSO which influences weather patterns around the world in two-to-seven-year phases defined by the temperature of the equatorial Pacific Ocean. El Niño is the ‘hot’ phase of the cycle, it moves heat from the oceans to the atmosphere and redistributes the world’s rainfall, generally bringing drought to areas near the equator and above-average rain to others. The question that most people want answered is: Which weather pattern will occur where and how strong will it be?
Precipitation patterns from past El Niño’s are not predictive. Although there is often heavier rainfall on most coastal areas of the United States, an El Nino can also bring an unusually dry winter.
Source: CLIMATE.US, Data from nClimgrid.
The atmosphere is a chaotic physical system, so weather models can only predict what local conditions will be about two weeks ahead. Climate modelers try to make more general predictions months in advance, honing the forecasts as the weather pattern develops. Climate model forecasts begin to firm up after the Spring Predictability Barrier (March to May), so news of a possibly strong El Niño starts to hit the media in summer as it did this year. The models continue to refine their predictions monthly, using up to date measurements of Pacific Ocean surface temperatures, the strength of the trade winds and other real-time data.
Over 100 climate models have been built by researchers around the world. In order to predict a large-scale event like El Niño, the results of individual models are combined to make a risk assessment called a multi-model ensemble. The ensemble gives a range of probabilities that science communicators and journalists use to try to make predictions.
Daniel Swain, a weather and climate scientist at the University of California, is especially good at communicating about modeling and climate predictions. In this September 2026 video he walks the audience through what can be known and what can only be estimated as a probability until we are closer in time. The focus is on California, which is often strongly impacted by both ENSO phases.
All signs point to a super-strong, record-breaking El Niño.
According to Swain, sea level rise will be a big problem for the West Coast. The heated ocean water that characterizes El Niño will flow up the coast of Mexico in what’s called a coastally trapped Kelvin wave, fully extending up the southern California coast by around mid-October. The Kelvin wave will add about a foot of sea level rise to the approximately 6 inches of sea level rise caused by ocean warming since 1900. (See Swain’s graph of sea level rise in the video at 28:42) This does not include the short-term sea level rise events from storm swells and peak (king) tides that are expected later in the winter.
El Niño itself, as measured by Pacific water temperatures, will peak around December 2026, but weather effects caused by El Niño are lagging indicators and are expected to be strongest in early 2027.
The 2026-27 El Niño event itself is already record-breaking in terms of ocean temperatures, and the multi-model ensembles show a high probability that there will be very heavy rainfall in California during this El Niño. (Jump to the 48-minute point in the Swain video.)
A Newsweek article features September maps issued by NOAA that predict warm winter temperatures across the northern part of North America and above average precipitation in a band across the southern United States.
The ocean heat wave that El Niño brings is already affecting marine ecosystems along the west coast of the Americas. This Nature article reports that anchovy season in Peru has been cancelled, as the fish head for deeper, cooler water. Phytoplankton populations in the Pacific are lower, which will have ripple effects up the food chain. A hot, dry weather pattern has appeared in regions near the equator and there are worries about harvests and food security.
Is this El Niño stronger because of climate change? Climate models have not been able to answer this yet (Berkeley Earth video at 28 minutes) but its effects are superimposed on long-term climate impacts such as sea level rise and higher intensity of rainfall and drought. Since El Niño moves heat from the oceans to the atmosphere a temporary jump in global atmospheric temperatures is expected and will probably make 2027 the hottest year on record.