The Harmattan is a seasonal wind which blows across Northwestern Africa every year from November through March, at intermittent strengths. This wind has become famous with visitors to the area, who often struggle with Harmattan conditions, and residents often speak ill of it, since it can interrupt commerce and daily life for days. The dry wind lowers the humidity, which can lead to hot days and cool nights.
This famous wind blows from North to South, working its way across the Sahara to the Gulf of Guinea. Along the way, it tends to pick up sand and dust, turning into a very drying, dusty wind. When the Harmattan really gets going, the dust can create a cloudy haze which can sometimes intensify into an actual sandstorm. Visitors to the area have been taking note of the Harmattan since at least the 17th century, when the word "Harmattan" entered the English language.
"Harmattan," incidentally, appears to come from the Twi language of Ghana. Some people have suggested that it may be related to the Arabic word haram, which means forbidden. In any case, when the dust in this wind gets thick enough, it can bring life to a halt, as people cannot travel outside to trade or socialize. Harmattan winds have also notoriously interrupted flight schedules and caravans across the Sahara.
When the Harmattan is more mild, it can create a delicate haze which looks almost like smog. Much like smog, the Harmattan haze can look strangely beautiful, especially at dawn and dusk, when the light captures the particles in the air, creating a strangely diffused look. This seasonal wind can also cause dramatic weather conditions, when it interacts with other winds and weather systems. Harmattan winds can even cross the Atlantic; dust from the Sahara has been reported in the Americas after a particularly brisk Harmattan.
This famous wind is one among many named winds around the world, from the Santa Ana to the monsoon. These regional winds often play a major role in people's lives, so it is perhaps not surprising that they have been named, and that a mythology often builds up around them. North Africans, for example, often say that the Harmattan wind brings about bad tempers and poor decision making, as people grow irritated with the days on end of dry, dusty wind.