What will the peak RONI be for the 2026–27 El Niño?

Rules and resolution

This market resolves based on the peak RONI — the single highest Relative Oceanic Niño Index (RONI) value reported by NOAA's Climate Prediction Center (CPC) across the overlapping three-month seasons ASO 2026, SON 2026, OND 2026, NDJ 2026-27, and DJF 2026-27, as published in official NOAA CPC RONI updates (https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso/roni/). See each individual market for its bracket and full resolution terms. This market may resolve immediately once NOAA has published a RONI value that determines the peak: the "Over 2.5" outcome resolves "Yes" as soon as any listed season reaches +2.5°C or above. Any other outcome will not be confirmed until NOAA publishes the DJF 2026-27 value, since RONI can still rise in a later season and DJF captures El Niño's typical peak-strength window. The first published RONI value for each listed season is final and governs resolution; no subsequent revision to a season's value will change the outcome once that season's first value has been published. If CPC's RONI dataset is permanently discontinued, other information from NOAA may be used.

Resolution source: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso/roni/

Data source and freshness

Odds, volume, and liquidity come from live Polymarket order books. Prices update continuously while trading is open; the figures above reflect the most recent refresh. Probabilities are market prices — what traders collectively pay for a $1 payout if the outcome occurs — not editorial forecasts.