Legend:
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 |
Moses/LU | 45.8mm in 60 minutes |
19.8 mm in just 10 minutes | |
Magadino/Cadenazzo/TI | 39.3mm in 60 minutes |
Torricella/Crana/TI | 37.3mm in 60 minutes |
Cham/ZG | 24.9mm in 30 minutes |
of which 14.2 mm in just 10 minutes | |
Payerne/VD | 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 | 5mm | |
10 mins | 7mm | 41.0 mm on June 11, 2018 in Lausanne/VD |
20 minutes | 10mm | |
30 minutes | 12mm | |
60 minutes | 16mm | 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.