Heavy rain – When the sky opens its floodgates – Meteo


Archive image Thunderstorm rain over Lake Thun

Heinrich Kuhn

On Friday it poured like rain

A thunderstorm zone brought large amounts of rain in places on Friday. As always with thunderstorms, the regional differences were large. Some of the rain totals were in the record range. In Cham, for example, within 10 minutes since measurements began in 1993, it has only rained twice as much as today’s 14.2 mm. In the Magadino plain in Ticino, almost 60 percent of the average June rain fell in 24 hours – 20 percent came together within just one hour: thunderstorms have passed here repeatedly since the night. In other areas, such as the very south of Ticino, the amount of rain was modest.

measuring station amount of rain


45.8mm in 60 minutes

19.8 mm in just 10 minutes


39.3mm in 60 minutes


37.3mm in 60 minutes


24.9mm in 30 minutes

of which 14.2 mm in just 10 minutes


12.3mm in 10 minutes

How is heavy rain defined?

According to the scientists Egli and Weischet, the following values ​​apply as reference points for Europe. The 10-minute and hour records in Switzerland clearly show that the usual definition can be exceeded many times over in extreme cases.

duration amount of rain Rain record Switzerland

5 minutes


10 mins


41.0 mm on June 11, 2018 in Lausanne/VD

20 minutes


30 minutes


60 minutes


91.2 mm on August 28, 1997 in Locarno/TI

Welcome water

Of course, heavy rain is locally too much of a good thing. There is a risk of flooding and landslides. But in general, the rain is urgently needed, especially in the south, where there is almost no meltwater this spring and summer. After all, the record-low water levels of Lago Maggiore and Lago di Lugano have already risen by a few centimetres. In most cases, however, heavy thunderstorms only lead to a short-term rise in water levels and no general relief from the drought.

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