What is the harmattan and where does it blow?

The harmattan is a cool, dry trade wind that blows from the northeast or east across the western Sahara and western Africa.1

Occurring primarily from late November to mid-March, this wind is notable for carrying significant amounts of dust across the region and hundreds of kilometers out over the Atlantic Ocean. Its arrival can cause a sharp drop in air temperatures, sometimes reaching as low as 9 °C (48.2 °F). During the summer, the harmattan is forced to higher altitudes by the southwest monsoon, and the interaction between these two air masses can occasionally result in tornadoes.1