Forecasters have steadily raised the likelihood that the developing El Niño will become exceptionally powerful, with the latest outlook giving it a greater than 90 percent chance of reaching “very strong” strength during fall and winter. The National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Center’s (CPC) forecasts have changed substantially since March, when El Niño had not yet developed and its potential strength remained uncertain. By this month, the agency said the event was strengthening and had a 69 percent chance of exceeding every previous El Niño in records dating to 1950 during the October-to-December period.
El Niño is the warm phase of the El Niño-Southern Oscillation, or ENSO, a recurring Pacific climate pattern that can affect weather worldwide. Its counterpart, La Niña, is the cool phase of the cycle. Typical El Niño effects can include stormier weather across the southern U.S., drier conditions in some northern areas and changes in hurricane activity, although NOAA stresses that impacts are not guaranteed everywhere.
It is commonly used to describe an exceptionally strong event. They added that a strong or "super" El Niño was “a virtual lock,” at that point. On March 12, the CPC said a transition from La Niña to neutral conditions was expected within a month.
Neutral conditions were favored through May to July, with a 55 percent probability, before El Niño was projected to emerge during June to August with a 62 percent chance. Forecasters expected it to persist through at least the end of the year but said its potential strength was highly uncertain. At that stage, there was a 1-in-3 chance of a strong El Niño during October to December.
By April 9, neutral conditions had arrived and were favored through April to June with an 80 percent chance. The CPC gave El Niño a 61 percent chance of emerging during May to July and said it was likely to persist through at least the end of 2026. Possible outcomes ranged from continued neutral conditions to a very strong El Niño, with the latter carrying a 1-in-4 chance.
The May 14 discussion raised the probability of El Niño developing during May to July to 82 percent. The CPC also gave it a 96 percent chance of continuing through the December 2026-to-February 2027 period. However, the agency said uncertainty over its peak strength remained substantial, with no individual strength category assigned more than a 37 percent probability.
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