Official NOAA Relative Oceanic Niño Index (RONI) Outlook
Issued September 2026
The values show the forecasted range of Relative Oceanic Niño Index (RONI) values for 9 upcoming, overlapping 3-month seasons (each letter represents a month, F = February). The color shading shows the forecast ranges, with the darkest color shading indicating that there is a 50% chance that the forecasted RONI values will remain between the RONI values displayed. There is a 90% chance that forecasted RONI values will remain between the upper and lower edges of the lightest color shading. The middle color shade provides the RONI forecast range with a 70% chance. Alternatively, the table provides RONI values corresponding to the various percentiles displayed in the image.
The official outlook is determined by a ~10 member team, using available insights from multiple models (multi-model ensembles) and the latest observations using climate reanalysis, in situ measurements, and satellite data.
Forecasts are verified using the Relative Oceanic Niño Index (RONI). The 1991–2020 climatological base period is used to define the departures.
Large positive or negative values of RONI do not necessarily correspond with the strength of the influence or expected impacts. Stronger El Niño and La Niña events often tend to be accompanied by higher certainty in the expected El Niño or La Niña impact, but never guarantees them (e.g. higher chances of above-average precipitation in a certain region of the country). Please refer to CPC's official seasonal outlook for chances of temperature and precipitation for upcoming seasons.
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