North Sea reaches record average temperature of 11.6°C

The North Sea reached a record average surface temperature of 11.6 degrees Celsius in 2025, the highest since measurements began in 1969, according to data from the Federal Maritime and Hydrographic Agency (BSH). This temperature is nearly one degree higher than the long-term average recorded between 1997 and 2021.

The warming trend is not limited to the surface; the total heat content of the North Sea has also reached a record high. The Baltic Sea also recorded its second warmest year on record in 2025, with an average temperature of 9.7 degrees Celsius.

Extreme weather events, specifically marine heatwaves, have become more frequent. Near the island of Helgoland, stations recorded 66 days of marine heatwaves by early September. Experts warn that rising temperatures lead to shifting habitats, the spread of non-native species, increased risks of harmful algal blooms, and oxygen depletion.

Additionally, the BSH reports that rising sea levels continue to impact German coasts, with rises of over 25 centimeters in Cuxhaven and nearly 20 centimeters in Warnemünde since 1900. While long-term warming is evident, the agency noted that specific weather patterns can still result in significant ice formation, such as the strong ice winter observed in 2025/26.