The best time to travel in the Karoo is between May and September. During the day, it is pleasantly warm and sunny (20 - 25 degrees C), and at night it gets cool enough for a good sleep.
The Karoo from a Khoikhoi word, possibly garo "desert" is a semi-desert natural region of South Africa. There is no exact definition of what constitutes the Karoo, and therefore its extent is also not precisely defined. The Karoo is partly defined by its topography, geology, and climate — above all, its low rainfall, arid air, cloudless skies, and extremes of heat and cold. The Karoo also hosted a well-preserved ecosystem hundreds of million years ago which is now represented by many fossils.
The Karoo formed an almost impenetrable barrier to the interior from Cape Town, and the early adventurers, explorers, hunters and travellers 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 50–250 mm, though on some of the mountains it can be 250–500 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 large game, sometimes in vast herds.
Today sheep thrive on the xerophytes, though each sheep requires about 4 hectares of grazing to sustain itself.