Record marine heatwave pushes Mediterranean Sea surface temperatures to 30°C (86°F) off Spain
Sea surface temperatures in the western Mediterranean Sea reached up to 30 °C (86 °F) in early July 2025, with anomalies of 5–6 °C (9–10.8 °F) above average under strong to severe marine heatwave conditions.
Sea surface temperature anomaly map for the week 29 June to 5 July, 2025. European Zone. Credit: Mercator Ocean International
Strong to severe marine heatwave conditions are ongoing in the western Mediterranean Sea as of July 5, with some localized regions experiencing extreme anomalies. Mean sea surface temperatures (SSTs) are currently around 26 °C (78.8 °F), exceeding the 1982–2023 climatological norm by 3–6 °C (5.4–=-10.8 °F).
SSTs off the coast of Spain have reached 30 °C (86 °F), a record high for this early in the summer. The Balearic, Ligurian, and Tyrrhenian Seas are registering widespread anomalies of 5–6 °C (9–10.8 °F) above baseline. By contrast, the eastern Mediterranean has shown slight weakening of anomalies but remains elevated.
The Copernicus Marine Service forecasts continued severe marine heatwave intensity in the western basin. Models indicate that the situation may persist through mid-July.
This warming poses significant threats to marine ecosystems, including coral reefs, mussel beds, sea grasses, and plankton populations, many of which are sensitive to small temperature shifts. Researchers report disrupted reproductive cycles, increased mortality, and structural ecological changes.
Beyond ecological damage, warm seas influence atmospheric conditions. Elevated SSTs enhance moisture content in the air, increase surface humidity, delay nighttime cooling, and heighten the risk of convective rainfall and inland flooding months after.
References:
1 Mediterranean Marine Heatwave brings water temperatures at record levels – Severe Weather EU – July 30, 2025
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