Swiss drought persists as jet stream stays far north

Switzerland is experiencing an exceptionally dry, sunny and warm September, with little significant rain expected before the end of the month, SRF reported. Meteorologist Jan Eitel said the jet stream has often remained far to the north, allowing the Azores high-pressure system to extend into central Europe.

Normally in September, wetter winds from the Atlantic reach Switzerland, or föhn conditions force warm, humid air from the Mediterranean out over the southern side of the Alps. Neither pattern has dominated this year. As a result, temperatures have been three to five degrees above average, while conditions have been unusually dry and sunny.

The dry spell is highly unusual from a meteorological perspective. Apart from a wetter period between September 6 and 9, high-pressure conditions have continued to dominate. From September 1 to 22, many parts of Switzerland recorded only 10 to 20 percent of the average rainfall for the period from 1991 to 2020. The Alps received somewhat more, at 30 to 50 percent of average rainfall. The Engadin, Puschlav and Münstertal recorded the most, with 60 to 90 percent of average rainfall.

Airolo in the canton of Ticino was the driest location, recording about 5 millimetres of rain. In an average September, it receives 190 millimetres. Geneva and Basel recorded only 7 to 10 millimetres, equivalent to just under one watering can of water per square metre.

The dry, sunny and unusually warm weather is expected to continue for now. Temperatures could reach about 26 degrees at the weekend. Low-pressure systems may approach around the turn of the month, but current forecasts do not indicate a prolonged period of rain. The dry conditions are therefore likely to continue for some time.