Overview
- Forecasters reported a rapid intensification in mid‑September with NOAA saying there is over a 90% chance of a very strong event this autumn–winter and about a 75% chance it will be the strongest since 1950.
- Observations show sea surface anomalies up to roughly 3–3.5°C in Niño regions and pronounced subsurface heat, signals that forecasters use alongside the RONI and ONI indices to track real‑time and seasonal El Niño strength.
- Peru’s ENFEN raised the probability of an extraordinary coastal 'El Niño Costero' to 85% for September and kept an official coastal alert through early 2027, while Senamhi warns of record summer heat in Lima with daytime highs near 36°C and heat indices up to 38°C.
- Governments and sectors are acting: Peru’s Education Ministry is prioritizing repairs for more than 8,000 school sites, seeking funds for 1,500 modular classrooms, and agencies across Mexico, Argentina and the U.S. are issuing regional advisories for agriculture, coasts and water management.
- Historical context matters because past strong El Niños produced very different regional outcomes; climate change has raised ocean baselines, which complicates comparisons and increases the risk that this event will amplify floods, droughts, coastal erosion and fisheries shifts.