The 1997-98 El Niño remains, by most measures, the strongest event of the 20th century and one of the strongest in the full instrumental record dating to 1950. It's the reference point every "Super El Niño" comparison gets measured against — including the one currently developing.
How It Unfolded
1997's event developed unusually fast, building from neutral conditions in early spring to a clearly established El Niño by summer — a speed of onset some forecasters have compared to what's been observed in 2026. By autumn, Niño 3.4 anomalies were already well past the "strong" threshold, and the event peaked above +2.0°C in the November-December-January window, qualifying as "very strong" by NOAA's current classification standards.
Globally, the impacts were severe: catastrophic flooding across Peru and Ecuador, devastating drought and wildfire conditions across Indonesia and parts of Southeast Asia, an unusually mild but wet winter across the southern United States, and a measurable bump in global average temperature that helped make 1998 the warmest year on record at the time.
Why Forecasters Keep Citing It
1997-98 set the template for what a "textbook" Eastern Pacific-dominant Super El Niño looks like: rapid spring onset, a clean winter peak, and a fast decay the following spring. When NASA scientists say 2026's western Pacific sea-surface-height pattern "looks similar to 1997," this is the event they're referencing — and it's exactly why the eastern Pacific's slower pace this year (see our Sentinel-6 coverage) is being watched so closely. If 2026 catches up to 1997's eastern Pacific pace, it's in rare company.