2027 is the year this El Niño lands on the planet.
The tropical Pacific pours heat into the atmosphere as an El Niño peaks, and the global average temperature follows a few months later. An event that peaks around Christmas therefore does most of its warming in the calendar year after: 1998, 2016 and 2024 were each the warmest year then measured. This event is forecast to be the strongest on record, so the question is not whether 2027 will be very warm but how likely it is to beat 2024, and how sure anyone can be.
This page builds its own forecast from four temperature records and the Copernicus ENSO forecast, and shows every choice it made. Compare Zeke Hausfather's Climate Dashboard and celsius.earth/predict.
The planet answers months later
Global temperature around a strong El Niño
Average of the 10 strong El Niños since 1957, in months from the December of the peak winter. The warming trend is removed first (a 10-year running mean), so this is the El Niño's own bump.
How long each part of the system takes
Correlation with Niño-3.4 when each series lags it by 0 to 15 months (1979–2025, trends removed).
The odds for 2026 and 2027
Global temperature, month by month, with the forecast through 2027
What the 2027 number is made of
How much the answer depends on the choices
Chance 2027 is the warmest year, re-run with one choice changed at a time.