Since measurements began in 1969, a new record average temperature of 11.6 degrees Celsius has been reached in the North Sea. This was announced by the Federal Maritime and Hydrographic Agency (BSH) in Hamburg. This means that the surface temperature in 2025 was 0.9 degrees above the long-term average for the years 1997 to 2021. The warming trend is also continuing in the deeper water layers, particularly in the southern North Sea and in the German Bight.

The Baltic Sea is also continuing to warm. There, 2025 was the second warmest year since the BSH data series began in 1990. The average surface temperature was 9.7 degrees Celsius, 1.1 degrees above the average for the years 1997 to 2021.
According to the BSH, the data not only shows long-term developments, but also new extremes. For example, a marine heatwave lasting 55 days was recorded in the Baltic Sea in spring 2025 - an unprecedented event. At the same time, the ice winter of 2025/2026 made it clear that extreme cold phases can continue to occur, particularly in the Baltic Sea, despite a climate that is becoming warmer in the long term.

kdk, Tagesschau

Photo: Warm North Sea water, only fun for children. kdk