While not dangerous, Luxembourg's skies will turn rather hazy as of mid-morning til late in the afternoon. It may also impair general air quality, with a high concentration of aerosols.
The Copernicus Atmosphere Monitoring Service measures an Aerosol Optical Thickness of close to 1. An optical thickness of less than 0.1 (palest yellow) indicates a crystal clear sky with maximum visibility, whereas a value of 1 (reddish brown) indicates very hazy conditions.
The northern wind coming from the Saharan Desert, called Sirocco, is a frequent phenomenon that often occurs in spring and autumn. Sometimes the sand carried does not reach Europe, as rain above the Mediterranean ensures its deposit prior to reaching the mainland.
