Because southern Africa is such a large area, with each region offering different seasonal benefits, the time you go should help determine where you go.
South Africa
The summer months (Nov-Feb) tend to attract the majority of visitors (particularly from Europe). Fortunately, the country is big enough to absorb these increased numbers without causing the discomfort most people associate with busy seasons. Be aware, however, that accommodations' 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 in December and over the Easter long weekend. Spring (Sept-Oct) and autumn (Mar-Apr) are considered by many to be the best times to visit, when temperatures are not quite so high (the balmy to baking days of Feb-Mar are particularly popular in Cape Town). Winter (June-Aug) brings substantial benefits, too: July to November are the months when the southern right whales migrate to the Cape's southern coast, providing guaranteed sightings. 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 year-round in both these areas. Cape Town gets winter rainfall during what it calls its green season (May-Aug), though there are always sunny breaks. Thanks to the year-round sunshine that the Garden Route and Karoo enjoy, any time is a good time to tour this region.
Note that June to October is peak season in the Delta, Botswana, when the game-viewing is best and lodges charge top dollar for the privilege.
The Climate -- Depending on where you are, average maximum temperatures can vary from 80°F/27°C (Cape Town) to 90°F/32°C (Kruger National Park) in the summer, and from an average 69°F/21°C (Cape Town) to 77°F/25°C (Durban) in winter. While summer is the most popular time, high humidity in KwaZulu-Natal can make for muggy days, and gale-force winds often occur in Cape Town and Port Elizabeth. Winter visitors would be well advised to pack warm clothes -- despite higher average temperatures than in the United States or Europe, South Africa is simply not geared for the cold, and insulation and central heating are low on the priority list. Temperatures in the interior fluctuate wildly in winter; you're best off layering.
Rainfall -- South Africa is generally considered an arid region, with two-thirds of the country receiving less than 500 millimeters (20 in.) of rain a year. In the interior, rain usually falls in the summer, and spectacular thunderstorms and the smell of damp earth bring great relief from the searing heat. The Garden Route enjoys rain year-round, and in Cape Town and surrounds, the rain falls mostly in the winter, when the gray skies are a perfect foil for the burnt-orange strelitzias, pink proteas, and fields of white arum lilies -- not to mention the perfect accompaniment to crackling fires and fine South African red wines.
Holidays -- If you are traveling during the South African school holidays (check exact dates with South African Tourism), make sure you book your accommodations well in advance. Flights can also be impossible, particularly over the Christmas holidays. Easter holidays (usually the end of Mar to mid-Apr) can also be busy, while the Kruger is almost always packed during the winter vacation (mid-June to mid-July). There's another short school break in spring, from late September to October 7.
Public holidays in South Africa include New Year's Day; March 21 (Human Rights Day); Good Friday, Easter Sunday and Monday; April 27 (Founders/Freedom Day); May 1 (Workers Day); June 16 (Soweto/Youth Day); August 9 (Women's Day); September 24 (Heritage Day); December 16 (Day of Reconciliation); Christmas Day; and December 26 (Boxing Day).
Zimbabwe/Zambia
Zimbabwe and Zambia's climate are similar to that in South Africa's northern provinces, with a summer rainy season and most of the rainfall occurring between December and mid-March. Summers are warm to hot (late Oct to Dec can be uncomfortable), and winters are mild. Malaria is still a danger in many areas, there are tsetse flies in parts of the Zambezi Valley and in the southeast, and be aware that certain rivers, lakes, and dams are infected with bilharzia. Victoria Falls are often at their fullest from January to mid-April, at the end of the rainy season, though this is also when the mist created by the falling water may obscure the view, and malaria-carrying mosquitoes are at their most prolific. Temperatures are pleasantly reduced from May to October (81°F/27°C). Many think the best time to see the falls is from August to December, when the view is clearer (though the flow of the water is at its lowest). From June to December is high season for many of the upmarket lodges, which raise their prices during these months. You are unlikely to be affected by public holidays.
Botswana
Botswana has a pleasant subtropical climate with low humidity. Rain falls during the summer months, from November to March -- this is a great time to visit the delta if you're interested in birds and plants, but it can get very hot. From April to September, the days are mild to warm, but temperatures drop sharply at night and early in the morning, particularly around June and July. Most consider these 2 months the best time to visit the delta, when the rain that falls on the Angolan bushveld plains seeps down to create what is referred to as the "flood." At this time, waterlilies bloom, countless aquatic creatures frolic in the water, and a huge diversity of game from the surrounding dry areas moves into the delta. You are unlikely to be affected by public holidays.




