On 6 February 2021, across parts of Switzerland, people awoke to a strange yellowish light and brown skies.
The strange light and brown sky is caused by sand from the Sahara desert. It is a well known meteorological phenomenon that occurs around three times a year in Switzerland, according to SRF Meteo.
Areas currently most affected by it are in western Switzerland and include Geneva, Vaud, Valais and Fribourg.
According to SRF Meteo, the sand came mainly from the north-west of Africa, a region containing Mauritania, Mali and Algeria. Most of the sand is floating airborne at between 2km and 5km from the ground, according to the weather service. It takes between 2 days and a week for the dust to travel from the desert to Europe. The largest particles land on the ground while the smallest remain airborne and continue their journey northward.
The phenomenon accompanies a warm air weather system known as the Foehn.
SFR Meteo (in German)