Africa isn't ALWAYS sunny. In Cape Town there are three main seasons: Summer, Winter and Windy.
Windy season is usually (but not always) from about September through March. Summer is November through March/April. Winter is June to end August officilally. 1 September is the 1st day of Spring, but can still be chilly by our standards. By European standards, it is summer!
Summers are beautiful and hot but expect that every other day could be varying levels of wind. For wind sport enthusiasts, the weather in Cape Town is ideal. Winters can be stormy - hence the nickname "Cape of Storms". So don't expect to lay on the beach in June - likely to be grey and rainy. Having said that we get beautiful crystal clear days with no wind, which are fantastic.