Heatwaves of 'record intensity': the Mediterranean Sea experienced its hottest June ever recorded

By The New Obs with AFP

Published on July 8, 2025 at 5:13 p.m.

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The Mediterranean Sea has just experienced its hottest June on record, with marine heatwaves of "record intensity" affecting 62% of its surface area, the Mercator Ocean International organization announced on Tuesday, July 8.

The average surface temperature of this enclosed sea, which is warming faster than the rest of the ocean, reached an average temperature of 23.86°C in June, beating its previous record of June 2022 (23.72°C), according to Mercator Ocean International, operator of the European Union's Copernicus Marine service.

Almost the entire Mediterranean basin (88%) experienced above-average temperatures in June, particularly in its western half, which experienced marine heatwaves "reaching records in intensity, duration and extent" , according to a press release.

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Thus, 62% of the surface of the Mediterranean Sea was affected by marine heat waves in June 2025, "the highest extent ever recorded" , specifies Mercator.

"The month of June was characterized by the presence of a heat dome over Europe, which had a significant impact on the Mediterranean Sea with an absence of clouds, an absence of wind and an increase in solar radiation," oceanographer Simon Van Gennip described during an online press briefing.

Marine heat waves can fuel hurricanes and cyclones, degrade ecosystems and cause mass mortality of marine species , he recalled, specifying that corals, gorgonians and bivalves (mussels, in particular) were the most threatened species in the Mediterranean.

The first half of 2025 was also the hottest on record in the Mediterranean. By July 12, Mercator predicts a significant decrease in marine heatwaves in this region, thanks to a surge in winds that should better distribute heat to the deep ocean layers.

As for the global ocean, this year it experienced its third warmest June on record after 2023 and 2024, according to Mercator, with an average surface temperature of 20.75°C. One-fifth of the global ocean's surface was affected by intense marine heatwaves at the end of June. The oceans play a climate-regulating role by absorbing 90% of the excess heat generated by human activities.