The summer months (from November to February) tend to attract the majority of visitors (particularly from Europe). However accommodation prices do increase in summer, some by as much as 80%; and if you dislike crowds you should try to avoid South Africa's busiest school holidays, which take place over December and the Easter long weekend. Many consider Spring (September and October) and autumn (March and April) to be the best times to visit, when temperatures are not quite so high (the balmy to baking days of February and March are particularly popular in Cape Town).

Whales migrate to the Cape's southern coast from July to November. This period more or less covers the Winter (June to August) and guarantees fabulous sight seeing. At the same time, May to August are considered the best months for sighting big game: the foliage is less dense, malaria areas offer a lower risk, and many of the private game reserves drop their prices substantially. 

 This is also a good time to visit Botswana and Zimbabwe, though Victoria Falls will not be in full flood (Zimbabwe is a summer rainfall area), and malaria remains a high risk all year round in both these areas. Cape Town gets winter rainfall during what it calls its Green Season (from May to August), though there are always sunny breaks. Any time is a good time to tour this region, thanks to the  sunshine that the Garden Route and Karoo enjoy year-round.