Swiss lakes reach record high temperatures

Record temperature rise in Swiss lakes Keystone-SDA

Swiss waters have warmed up considerably due to the hot weather. Over the last two weeks, lake temperatures have risen by an average of five degrees. According to the Meteonews weather service, this is an all-time record.

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If we refer to the standard established using the average for the years 1983 to 2024, the increase represents between four and seven degrees. Meteonews attributes this increase almost entirely to the heatwave that has been affecting the country for almost two weeks.

In French-speaking Switzerland, the temperature of Lake Geneva has risen to 26 degrees, four degrees warmer than in mid-June and five degrees warmer than the average for the last 41 years.

Lake Neuchâtel followed the same trend, with slightly cooler water (25), but also five degrees warmer than both the second half of June and the 41-year average.

Lake Biel came out on top, with a temperature of 26 degrees, 6 degrees warmer than last month and its average over the last 41 years.

Lugano, the warmest

The highest temperature recorded by Meteonews was in Lake Lugano, at 28 degrees, 5 degrees warmer than the 41-year average.

Lake Walen, in the cantons of St Gallen and Glarus, has seen its temperature rise to 25 degrees, 7 degrees above its average from 1983 to 2024.

Meteonews warns, however, that the situation is extremely variable and that the weather forecast for the upcoming weekend and early next week could cause these values to fall.

Rivers also affected

Rivers also showed significant deviations from normal temperatures. The Aare near Bern, the Reuss near Lucerne and the Rhine near Laufenburg have never been so hot.

As well as the heat, there are other reasons for the high temperatures, according to Meteonews. The weather service cites poor snow cover in the mountains at the start of the warm season.

Fauna and flora affected

The impact of this rapid warming of the country’s waters is visible on several levels, say the meteorologists. In addition to the relatively low water levels, some species of fish are finding it difficult to thrive in water that is too warm.

The growth of algae is also favoured in this context, leading to a reduction in the oxygen content of the water. The result is a blockage in the photosynthetic processes of aquatic plants, and the formation of toxic substances such as blue-green algae.

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Translated from German by DeepL/jdp

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