Intense heat which hit Western and Central Europe at the end of June additionally warmed the surrounding areas (mora). The water on the surface is more than 5 °C warmer than is usually the case for this time of year, according to data from the Copernicus Maritime Service.
If you are spending your summer on the Croatian, Montenegrin or Albanian coast these days, you have probably experienced this sea heat on your own skin: on the Copernicus map, which was created to depict the temperature deviations for June 29, the Adriatic is one of the areas painted in red shades. These colors suggest that sea temperatures are several degrees higher than typical, writes Jelena Kozbašić for the Klima 101 portal.
As Copernicus points out, the biggest deviations - of approximately 6 °C - are recorded in the western part of the Mediterranean Sea, especially in the Gulf of Lyon near the coast of southern France, as well as in the Ligurian and Tyrrhenian Seas along the western coast of Italy.
The north of Europe is not devoid of dark red shades either: the water is much warmer in the southern parts of the North Sea and in the Baltic Sea.
But the red sea waters around Europe at the very end of June are only part of the bigger picture...
Oceans never warmer
According to Copernicus data, the world's oceans suffered the warmest June in recorded history.
Last month, the average ocean temperature, excluding the polar regions, reached 21 °C, breaking the previous records set in June 2023 and 2024.
Since the beginning of this year, 2026, sea surface temperatures have been consistently elevated, with widespread marine heat waves affecting 82% of the oceans globally. With an average temperature of 20,94 °C, including the June record, it was the second warmest first half of the year for the world's oceans.
In addition to the central parts of the North Atlantic and the equatorial Pacific, the Mediterranean Sea stood out as one of the hotspots.
"These regional signals provide a clear picture of an ocean that is under continuous heat stress," said Simon Van Gennip, lead oceanographer at the Copernicus Naval Service.
Given that anthropogenic climate change and the natural El Niño will further warm the seas, more records could be broken in the coming months.
The summer temperatures of the Adriatic are getting higher
For decades, scientists have been recording the gradual warming of the sea throughout the Mediterranean, including the Adriatic, not only on the surface but also at greater depths.
As Dr. Natalija Dunić from the Institute of Oceanography and Fisheries in Split wrote for our portal, from the middle of the 20th century until today, an increase in temperature of 0,5 to 1,5 °C has been recorded, depending on the location and depth. Although changes are observed throughout the year, they are most pronounced in summer.
What is particularly worrisome is the fact that in the last twenty years the warming trend has accelerated: in the past, summer temperatures on the sea surface were around 25 °C, while today they often exceed 27 °C, and increasingly reach values higher than 29 °C in shallower areas.
In the age of climate change, the Mediterranean is one of the fastest warming sea basins in the world. The Adriatic Sea is particularly sensitive because it is shallow, semi-enclosed and strongly influenced by river flows and land climate.
Although rising sea temperatures extend the swimming season and are pleasing to some, others will say that the water is "sickly warm, like in a swimming pool". But our subjective feeling of bathing is not the only one that changes - moreover, although empirically confirmed, it is probably the most painless item.
The consequences are also felt in the quality of the sea, tourism and fishing. Thus, fishermen on the Adriatic will increasingly catch lionfish, an invasive species from the tropics that, partly thanks to the warming of the sea, has become domesticated and spread in the waters of Albania, Montenegro and Croatia.
In the end, the story does not stop at hooks and nets... The lionfish has no natural enemies here and threatens local ecosystems and species, and in the warmer Adriatic it is only one in a sea of threats.
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