Portugal goes into its storm season with the warmest ocean ever measured
Copernicus confirmed a global sea surface average of 21.1C on 22 August, beating the 21.09C set in March 2024. The month it happened in is the part that matters, and the mechanism the EU service describes reaches the Atlantic coast in autumn.
On 22 August the average temperature at the surface of the world’s oceans reached 21.1C. Copernicus, the European Union’s climate change service, has confirmed it as the highest daily figure on record, measured against the ERA5 dataset that runs back to 1979.
The previous record was 21.09C, set in March 2024. A hundredth of a degree is not, on its own, a story. The month is.
August is the wrong month for this
Oceans do not warm evenly through the year. The global peak normally lands in March and April, after the southern hemisphere summer, because that is where most of the planet’s water sits. August is supposed to be part of the cooling half of the cycle.
August is when the record fell. The best previous August figure was 20.98C in 2023, and this year came in 0.12 above it.
What Copernicus says comes next
A strong El Niño is forming in the tropical Pacific, adding heat to an ocean that has been warming for decades. The World Meteorological Organization expects it to strengthen over the coming months, and the Copernicus seasonal forecasting system suggests it could reach a scale not seen in several decades.
The service also sets out the mechanism that matters to anyone living with their back to the Atlantic. A warmer ocean transfers more heat and moisture into the atmosphere, which can intensify rainfall and some storm systems. That is not a forecast for any one country, and Copernicus does not offer it as one. It is the physics a storm season feeds on.
Portugal is still paying for the last one
Portugal is not yet finished with the previous season. Storm Kristin crossed the country in January, and seven months later the state was still widening the recovery programme. In August another 26 councils joined Territórios Resilientes, taking it to 82 municipalities and €80 million.
Portugal’s storm calendar usually opens in October and runs to February. What the 22 August record changes is not the certainty of any given storm. It is the size of the energy store the season starts with.
Image: C3S/ECMWF, Copernicus Climate Change Service (© European Union, 2026)