30 degrees on the weekend: Austrian water rescue warns against swimming in the lake despite record temperatures. 30 degrees on Saturday, April 6th and Sunday, April 7th is not yet suitable for swimming in Austria.
Even in Germany the water temperature remains too low for swimming. Immersing yourself in ice-cold water can cause cold shock. This triggers life-threatening reflexes in the body that lead to drowning. Cold swimming by people who are used to it can lead to failure to swim or hypothermia.