A La Niña event has developed in the tropical Pacific in August-September 2020, exceeding both oceanic and atmospheric thresholds. The latest forecasts from the WMO Global Producing Centers of Long-Range Forecasts indicate a high likelihood (90%) of tropical Pacific sea surface temperatures remaining at La Niña levels until the end of 2020, and a moderate likelihood (55%) for them to persist through the first quarter of 2021.