Namibia extends from 17°S to 25°S: climatically the range of the sub-Tropical High Pressure Belt, arid is the overall climate description descending from the Sub-Humid (mean rain above 500 mm) through Semi-Arid between <answer>300 and 500 mm</answer> (embracing most of the waterless Kalahari) and Arid from 150 to 300 mm (these three regions are inland from the western escarpment) to the Hyper-Arid coastal plain with less than a 100 mm mean. Temperature maxima are limited by the overall elevation of the entire region: only in the far south, Warmbad for instance, are mid-40 °C maxima recorded.
What is the semi-arid measurements in Namibia?
300 and 500 mm