PRESS RELEASE – Toulouse, 8 July 2025
June 2025 becomes the third hottest June on record globally. Record-breaking marine heatwaves of high intensity affect 62% of the Mediterranean Sea
Marine heatwaves are continuing to intensify and expand, with June 2025 setting new records for sea surface temperatures and heatwave extent across Europe and the global ocean, according to Mercator Ocean International, the EU’s Copernicus Marine Service operator. While some regions are showing signs of relief, others remain under severe thermal stress.
🔷 Key Highlights
- Mediterranean Sea: June 2025 was the hottest June ever recorded, with an average sea surface temperature (SST) of 23.86 ± 0.47 °C
- 62% of the Mediterranean Sea experienced strong or higher category marine heatwaves in June — the largest extent ever recorded
- 72% of the world’s oceans registered above-average temperatures on 30 June 2025, and 20% experienced marine heatwaves
- Marine heatwaves are increasing in frequency and severity, threatening marine ecosystems and coastal communities worldwide
🌍 Global Ocean – June & First Half of 2025 Overview
- June 2025 was the third hottest June on record globally, following 2023 and 2024, with a global average SST of 20.75 ± 0.07 °C
- 72% of the global ocean surface had SSTs above the long-term average (based on the 1993–2022 reference period)
- 20% of the global ocean experienced strong or higher category marine heatwaves by the end of June
- The global SST minimum for the first half of 2025, at 20.89 ± 0.06 °C, was the second warmest ever, just behind 2024 (21.04 ± 0.06 °C)
🌊 Mediterranean Sea
- Hottest June ever recorded, surpassing the previous 2003 record, with an average SST of 23.86 ± 0.47 °C
- 88% of the basin saw above-average temperatures; more than 60% of the region recorded monthly means at least +1 °C above normal, with nearly 30% exceeding +2 °C
- The Western Mediterranean was most severely impacted, with record-setting marine heatwave intensity, duration, and extent
- At peak intensity, 62% of the Mediterranean surface was under strong to severe heatwave conditions (compared to 40% at the same time in 2024)
- January–June 2025 was the warmest first half of a year ever recorded in the basin, with 88% of the area affected by high-intensity marine heatwaves
🌐 North Atlantic Ocean
- June 2025 was the third hottest June on record in the North Atlantic, with an average SST of 22.84 ± 0.20 °C
- 71% of the region experienced above-average SSTs, with the most pronounced anomalies near European and North American coasts
- The first half of 2025 also ranks as the third warmest on record, with 50% of the North Atlantic experiencing high-intensity marine heatwaves
📈 Weekly Forecast: 5–12 July 2025
Mediterranean Sea
- Western Basin: Heatwave intensity and extent are decreasing, shifting from strong/severe to moderate/locally strong
- Eastern Basin: Heatwave subsiding, with only a few moderate areas remaining
North Atlantic Ocean
- Heatwave weakening off Portugal but expanding mid-basin; intensity remains strong/severe
- North Sea: Heatwave decreasing; moderate to locally extreme patches persist
- Florida to mid-Atlantic: Shrinking near Florida, expanding mid-basin; intensity remains moderate to severe
📊 Media Resources
For more details and data visualizations, access the weekly MHW bulletins and monthly ocean temperature updates from Mercator Ocean International.
🛰️ Sea Surface Temperature Viewer (Copernicus Marine Service):
Viewer_SST_today
📣 Follow us on LinkedIn:
https://www.linkedin.com/company/mercator-ocean
📁 Access press materials:
Files – Mercator Ocean File Sharing Facility
🔗 Source: European Union, data from Copernicus Marine Service 2025 © Mercator Ocean
📞 Press Contact – Summer 2025
Laurence Collet
Corporate Communications & Press Relations, Mercator Ocean International
📧 press@mercator-ocean.fr
📞 +33 6 76 86 85 15
🌐 About Mercator Ocean International
Mercator Ocean International is a global leader in digital oceanography, delivering reliable ocean insights, forecasts, and analyses to advance science, policy, and societal needs. Founded in 1995 and headquartered in Toulouse, France, the organization employs 120 staff and is led by CEO Pierre Bahurel. As a registered European organization in France, it operates the Copernicus Marine Service on behalf of the European Union and is recognized as a global ocean forecasting center. Mercator Ocean also co-develops the European Digital Twin of the Ocean and hosts the coordination center of the G7 Future of the Seas and Oceans Initiative.
🔗 More info: https://www.mercator-ocean.eu/
🌊 About the Copernicus Marine Service
The Copernicus Marine Service is dedicated to ocean observation, monitoring, and forecasting. It is funded by the European Commission and implemented by Mercator Ocean International. The service delivers regular and systematic reference information on the physical and biogeochemical state of the ocean globally and across European regions. Mercator Ocean’s marine heatwave bulletins are based on Copernicus Marine data.
