La Niña is officially declared when central-eastern Pacific water temperatures persist at least 0.5°C below average.
Notes on verification
Confirmed by multiple NOAA sources (Climate.gov, PMEL) which consistently define La Niña by the 0.5°C below-average threshold in the Niño-3.4 region, persisting over multiple overlapping 3-month periods. Claim is a slight simplification but factually accurate. [tier=bronze indep_score=0.539 clusters=2 claim_tier=notable]
Sources
- Say Goodbye to a Historic El Niño and Hello to La Niña (seed:science_and_space)
- https://www.climate.gov/enso (corroboration)
- https://www.climate.gov/media/3359 (corroboration)
- https://www.pmel.noaa.gov/elnino/what-is-la-nina (corroboration)