As Namibia being a typical semi-desert the climate varies daily, with hot days and cool nights, it is recommended that you pack both summer clothing as well something warm for the evenings. It is advisable to pack a sweater and/or jacket as it becomes quite cool in the evenings and early mornings. Locals prefer dressing in layers with a shirt, light jersey and fleece top over the lot as it allows one to peel off or add as the day progresses. The weather is very unpredictable in Namibia so insure you never go about without something warm.
Although there have been wetter and drier periods the country remains an arid region, Namibia’s climate has probably been rather similar to what it is today for millions of years. The oldest sand dune deposits in the Namib Desert go back perhaps 13-18 million years, so the kind of dry conditions for their formation have been present for a long time.
Similarly, soils and salts concentrations in underground water suggest that, northern Namibia have been subject to patterns of sporadic flooding and high rates of evaporation similar to those occurring currently. Atlas of Namibia