If there are so many positive elements to our local climate, why is it that Namibia is labelled Arid? The reason lies in the fact that there are significant negative factors determining the general climate. First and foremost, Namibia lies within the climate range of the Sub-Tropical High Pressure Belt. This band of descending, drying air extends around the globe, both and north and south of the Equatorial or Tropical climate belt. This dry air climate generally restricts our rainfall expectations to those limited occasions when the wet, positive, influences can intrude.

This overall condition is enhanced when the ENSO (El Nino-Southern Oscillation) event occurs and upsets regular weather patterns on a global basis. Apart from restricting rainfall intensity, it also limits the regular occurrence of rain.
This last season, among others, provided yet another classic example.
Being on the western side of the sub-continent, Namibia's rainfall regime is dictated by the expected rise in summertime temperatures, developing the heat-low pressure area, and the ability of cooler air from the Atlantic to be advected inland towards this heat-inspired lower pressure area. This cooler air tends to block any westward drift of this system, thereby denying much of the land any access to the moist air on the eastern side of this anticipated summertime condition. The Rainfall Province criteria, highlighting the westward moving crest of the rainfall season cannot attain its full impact.
Hence the rainfall potential is thus reduced, but with adequate occurrence and intensity to place Namibia in the semi-arid range.
Africa is one continent with two Trade Wind deserts: the Sahara and the Kalahari. Yet as the eye tells the observer, while the Sahara is truly hyper-arid, we are better off, "semi-arid" as some authors, notably Professor Sharon Nicholson observed. Nevertheless, Namibia is the driest country in the southern hemisphere.