The ǃ’Aukarob formed an almost impenetrable barrier to the interior from Cape Town, and the early adventurers, explorers, hunters, and travelers on the way to the Highveld unanimously denounced it as a frightening place of great heat, great frosts, great floods, and great droughts.Today, it is still a place of great heat and frosts, and an annual rainfall of between 50 and 250 mm, though on some of the mountains it can be 250 to 500 mm higher than on the plains. However, underground water is found throughout the Karoo, which can be tapped by boreholes, making permanent settlements and sheep farming possible.
The xerophytic vegetation consists of aloes, mesembryanthemums, crassulas, euphorbias, stapelias, and desert ephemerals, spaced 50 cm or more apart, and becoming very sparse going northwards into Bushmanland and, from there, into the Kalahari Desert. The driest region of the Karoo, however, is its southwestern corner, between the Great Escarpment and the Cederberg-Skurweberg mountain ranges, called the Tankwa Karoo, which receives only 75 mm of rain annually. The eastern and north-eastern Karoo are often covered by large patches of grassland. The typical Karoo vegetation used to support the large game, sometimes in vast herds.