Every El Niño and La Niña event since 1950, classified by peak strength, based on NOAA CPC's ONI methodology, with RONI-era notes where the classification differs.
This table tracks every El Niño and La Niña event in the NOAA instrumental record back to 1950, classified by peak strength using the Oceanic Niño Index (ONI), three-month-average Niño 3.4 sea surface temperature anomalies versus the 1991–2020 base period. Where the newer Relative Oceanic Niño Index (RONI, NOAA's standard since February 2026) shifts a classification, that's noted separately. This page is updated as each new season's data is finalized by CPC.
El Niño: Weak 0.5–0.9°C · Moderate 1.0–1.4°C · Strong 1.5–1.9°C · Very Strong ≥2.0°C
La Niña: Weak −0.5 to −0.9°C · Moderate −1.0 to −1.4°C · Strong ≤ −1.5°C
| Event | Peak Season | Type | Strength | Notes |
|---|---|---|---|---|
| 1957-58 | NDJ | El Niño | Moderate | — |
| 1965-66 | NDJ | El Niño | Moderate | — |
| 1972-73 | NDJ | El Niño | Very Strong | First "Super El Niño" of the satellite-adjacent era |
| 1973-74 to 1975-76 | — | La Niña | Strong (multi-year) | — |
| 1982-83 | NDJ | El Niño | Very Strong | Caught forecasters off guard; reshaped ENSO monitoring |
| 1988-89 | NDJ | La Niña | Strong | — |
| 1991-92 | NDJ | El Niño | Moderate | — |
| 1997-98 | NDJ | El Niño | Very Strong | Peak ~+2.3°C; benchmark event, see our refresher |
| 1998-99 to 2000-01 | — | La Niña | Strong (multi-year) | — |
| 2007-08 | NDJ | La Niña | Strong | — |
| 2009-10 | NDJ | El Niño | Moderate | — |
| 2010-11 | NDJ | La Niña | Strong | — |
| 2015-16 | NDJ | El Niño | Very Strong | Peak ~+2.6°C; strongest on record per ONI, see our comparison |
| 2017-18 to 2022-23 | — | La Niña | Strong (near-continuous, "triple-dip") | RONI reclassifies this stretch as one continuous event |
| 2023-24 | NDJ | El Niño | Strong | One of the five strongest El Niños on record |
| 2024-25 | — | La Niña | Weak | Brief, weak event |
| 2025-26 | — | Neutral / Weak La Niña | Weak / Neutral | RONI read this stretch as definitive weak La Niña where ONI read neutral |
| 2026-27 | NDJ (forecast) | El Niño | Developing, Very Strong Likely | Advisory issued June 11, 2026; 60–63% NOAA probability of "very strong." See our live tracking coverage |
This table covers major/notable events and is not an exhaustive season-by-season listing of every weak/borderline fluctuation since 1950. For the complete official record, see NOAA CPC's ONI and RONI data files directly.
ONI (Oceanic Niño Index) is the raw three-month-average sea surface temperature anomaly in the Niño 3.4 region. RONI (Relative Oceanic Niño Index) subtracts the tropical-mean SST anomaly first, which accounts for long-term ocean warming and became NOAA's official standard in February 2026. Read our full RONI vs ONI explainer.
NOAA classifies El Niño strength by peak seasonal anomaly: weak (0.5 to 0.9°C), moderate (1.0 to 1.4°C), strong (1.5 to 1.9°C), and very strong (2.0°C or higher), measured as a three-month running average in the Niño 3.4 region.
That depends on the index, and the two now in use disagree. On ONI, the raw Niño 3.4 anomaly, 2015-16 is the strongest since 1950 at roughly +2.6°C for NDJ, narrowly surpassing 1997-98. On RONI, which subtracts the tropical-mean anomaly and became NOAA's official standard in February 2026, the 2015-16 peak is +2.4°C for NDJ 2015 and the record holder changes: Hausfather's analysis puts 1982-83 ahead. The difference is not a rounding detail. 2015-16 occurred on a warmer background ocean, ONI counts that warmth as part of the event and RONI does not, so the two indices name different decades as the record.
For live, current-season tracking, see the RONI panel and SST spaghetti chart on our dashboard.
What is being classified. Each event is classified on its peak overlapping three-month season, not on a weekly value and not on an annual mean. The Oceanic Niño Index is a three-month running mean of Niño 3.4 sea surface temperature anomalies against a fixed 30-year base period, so a single warm week never moves a classification. Weekly Niño 3.4 readings routinely run well above or below the seasonal index during a developing or decaying event, which is why a headline weekly number and a table entry can look inconsistent when they are measuring different things.
Two indices, two different answers. The strengths in the table above use the conventional ONI, because that is the index the entire 1950-onward record was built on and the only one that lets 1972-73, 1997-98 and 2015-16 be compared on equal terms. Since February 2026 NOAA CPC's operational ENSO products quote the Relative Oceanic Niño Index instead, which subtracts the tropical-mean SST anomaly before rescaling. In a decade of rising tropical background temperature RONI reads lower than ONI for the same ocean, so some recent events classify one category weaker on RONI than on ONI. Those are not revisions and not disagreements about the observations. Where the difference changes a classification it is noted in the table rather than silently averaged. The distinction is set out in full in RONI vs ONI.
Revisions are normal and this table follows them. The underlying ERSSTv5 analysis is reprocessed, so recent seasons are provisional: NOAA notes that newly published seasonal values can change for up to two months after first posting, and historical values shift when the base period is updated or the SST reconstruction is revised. Entries here are updated when CPC's published series changes. Because of that, this page should be read as a convenience view over NOAA's series, not as an independent authority. If a figure here and a figure in the CPC file below disagree, the CPC file is correct.
What this table deliberately does not do. It does not assign impacts to events, because a strength category says nothing reliable about what any single region experienced. It does not rank events by damage or by global temperature. And it does not extend before 1950, because the instrumental coverage that the ONI depends on is not comparable further back; reconstructions of nineteenth-century events such as 1877-78 carry uncertainty on the order of half a degree and are handled separately on the dashboard as a labelled analog rather than as a record entry.
Everything classified above is derived from NOAA's own published series. Those files are plain text, updated by CPC, and free to download directly. Working from them rather than from this page is encouraged.
If you cite this table, cite the NOAA series it is derived from as well. How sources are ranked and how errors are handled is set out in the editorial standards; corrections are logged at iamelnino.com/corrections.