The climate in the Klein Karoo is semi-arid, but in comparison to the Groot Karoo, the Klein Karoo receives much more rain, which falls almost exclusively in winter. The summers are hot and dry, daytime temperatures of more than 40 degrees are not uncommon. In winter, however, night frosts are not unusual and snow often falls on the Swartberg mountains across the valley.
The regional geology is an important factor for the fragile Karoo ecosystem. In large parts of the Karoo, sandstones are found. Sandstones are generally porous and therefore extremely permeable to water. Rainwater can quickly seep in and this increases the drought in the already low-precipitation region. In addition to the Fynbos, the Karoo also hosts a variety of succulent species, especially the midday flower plants. With sufficient winter rain, the plains cover themselves with flowers.