In the second half of June 2026, record-breaking heat was recorded not only on land but also in bodies of water. On 29 June 2026, for example, a water temperature of 30.2 °C was measured in Berlin’s Müggelsee – the highest temperature ever recorded for this lake. Near the shore, the temperature even reached 32.7 °C. But how do extremely high temperatures affect the lake and its wildlife? Researchers at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) provide an overview.