Spanish waters hit 'historic records' in May after extreme heatwave
State Ports' monitoring networks recorded all-time May temperature highs at 18 of their 29 buoys, from Galicia and the Cantabrian coast to the Mediterranean, peaking at 26.58°C off Mahon.
Published on 02/06/2026 - 17:47 GMT+2•Updated 18:26
From the Cantabrian Sea to the Balearics, Spanish waters ended May with temperatures never before seen at this time of year. Measurements taken by Puertos del Estado show record highs for this month along much of the coastline, after an episode of exceptional heat that also sent temperatures soaring on land.
According to the public body (source in Spanish), sea-water temperatures have reached "new records" in May, surpassing the previous maximum values recorded for this month. In total, 18 of the 29 buoys in its network registered exceptionally high temperatures.
Specifically, 12 of the 15 buoys in the Offshore Network and 6 of the 14 in the Coastal Network recorded their highest values since their respective data series began. The records were spread across much of Spain’s coastline. All the buoys located off Galicia and in the Cantabrian Sea reached all-time highs, as did numerous stations in the Mediterranean.
Record highs in the Balearics
The highest value across the whole network was recorded at the Mahón buoy, off Menorca, which reached 26.58 ºC on 27 May. It was followed by the Dragonera buoy, also in the Balearics, with 26.2 ºC on the 30th.
Other stations that broke monthly records included Tarragona, with 24.64 ºC; Cabo Begur, with 24.47 ºC; and Valencia, with 23.47 ºC.
The Coastal Buoy Network also recorded unprecedented May temperatures. Standout readings included 24.5 ºC measured in Tarragona on 30 May and 24.2 ºC registered in Barcelona the following day. Historic highs for this month were also reached at the stations in Bilbao, Pasaia, Gijón and Langosteira.
Among the deep-water buoys that set new records were those at Bilbao-Vizcaya, Cabo de Peñas, Estaca de Bares, Villano-Sisargas, Cabo Silleiro, Valencia, Tarragona, Cabo Begur, Dragonera and Mahón, according to figures released by Puertos del Estado.
A sea warmer than usual
These readings coincide with a spell of exceptional heat that affected Spain and much of Europe during the second half of May. According to the State Meteorological Agency (AEMET), some areas saw temperatures more typical of summer than of late spring, while in the Cantabrian Sea surface temperatures were between 1.5 and 2 ºC above the usual values for this time of year.
Experts point out that the ocean responds more slowly to atmospheric changes because of its high thermal inertia. This means that the heat stored in the water can persist for weeks even after air temperatures start to fall.
There is also concern about the potential impact on marine ecosystems. Persistently high temperatures can favour the development of marine heatwaves, alter the distribution of species, increase stress on certain habitats and affect economic activities linked to the sea, such as fishing.
Puertos del Estado manages one of Europe’s main oceanographic observation networks, made up of 15 deep-water buoys, 14 coastal buoys, 46 tide gauges and a network of high-frequency radars that make it possible to monitor in real time variables such as water temperature, waves, sea level and marine currents.
The World Meteorological Organization has recently warned that there is a high likelihood of global temperature anomalies continuing over the coming months, while various scientific bodies warn that the Mediterranean is among the regions most vulnerable to climate change.
