South Africa - Suitable Clothing
Most of your days you will want light, loose-fitting clothing. Cotton (or a cotton-rich mix) is cooler and more absorbent than synthetic fibers. For men, shorts are usually fine, but women should bear in mind that some ethnic groups regard visible thighs as a sign of availability. In sum, dress appropriately for your planned activities; if in doubt, ask.
Light cottons, with slightly heavier cottons or light woolens for evenings. In the evenings, especially for chilling rides in the back of safari vehicles, you will need something warm.
Nighttime temperatures in the winter months can be very low, especially in semi-arid and Highveld areas. If possible, dress in layers, taking along a light sweater (polar-fleeces are ideal) and a long-sleeved jacket, or a tracksuit, and a light but waterproof anorak.
Note that some excellent cotton safari-wear is produced and sold locally. Try the outdoor speciality shops in South Africa.
Finally, don't forget a squashable sun-hat. Cotton is perfect. Bring one for safety's sake, even if you hate hats, as it will greatly reduce the chance of your getting sunstroke when out walking.