Satellite measurements are showing a sharp surge in sea-surface temperatures across the tropical Pacific in recent months – the clearest early signal that El Niño is back. This powerful climate pattern, and its counterpart La Niña, can supercharge weather worldwide, amplifying extremes from heatwaves and droughts to torrential rainfall, floods and disrupted winter storm tracks, all on top of the effects of the already warming climate driven by human activity.

The animation shows early signals of the developing event, highlighting sea-surface temperature anomalies from 1–7 June 2026 compared to the 1991–2020 average for the same period.

Anomalies – the difference between current conditions and the long-term average – are used because El Niño often begins as a subtle shift away from what is considered ‘normal’, and these early changes are easier to see against a reference pattern. Although the temperature differences may appear small, the ocean stores and exchanges enormous amounts of heat, so even slight warming can indicate very large changes in the energy flowing between the ocean and the atmosphere.

Read full story: Pacific warming signals El Niño has stirred