Fifteen-minute Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) infrared dust index images are used to identify dust source areas. The observations of dust source activation (DSA) are compiled in a 1° × 1° map for the Sahara and Sahel, including temporal information at 3-hourly resolution. Here we use this data set to identify the most active dust source areas and the time of day when dust source activation occurs most frequently. In the Sahara desert 65% of DSA (March 2006 to February 2008) occurs during 0600–0900 UTC, pointing toward an important role of the breakdown of the nocturnal low-level jet (LLJ) for dust mobilization. Other meteorological mechanisms may lead to dust mobilization including density currents initiated by deep convective systems which mobilize dust fronts (haboobs) occurring preferentially in the afternoon hours and cyclonic activities. The role of the nocturnal LLJ for dust mobilization in the Sahara is corroborated by regional model studies and analysis of meteorological station data.