NOAA Climate Prediction Center
Oceanic Niño Index and ENSO monitoring
The operational definition of El Niño and La Niña events: the Oceanic Niño Index, a three-month running mean of sea surface temperature anomaly in the Niño 3.4 region, with the historical event record back to 1950.
Rights
- Commercial reuse
- Yes
- Redistribution
- Yes
- Derivative use
- Yes
- Attribution required
- No
- Restrictions
- Applies to material authored by US federal agencies. Third-party material carried within a federal product may be separately protected.
- Terms last checked
- 23 August 2026
Access and coverage
- Publisher
- NOAA Climate Prediction Center
- Geographic coverage
- Global — tropical Pacific index with worldwide teleconnections
- Temporal coverage
- 1950 onwards
- Update frequency
- monthly
- Formats
- csv, html
- Bulk download
- Available
- Registration required
- No
- Cost to Hydrionis
- Free
- Domains
- temperature, precipitation, drought