Don't worry too much about choosing when to go to Sun City: located at the edge of the southern Kalahari, this got-it-all resort sits under blue skies and is bathed in bright sunshine for most of the year and is a genuine year-round destination.
That said, you may want to avoid Sun City over the predictably busy South African school holidays (especially the Christmas/New Year period) and visitors to Sun City during the November - April summer will encounter the occasional afternoon thundershower or overcast day.
The bone-dry, clear-sky May to October winter period is often seen as the best time to visit Sun City if only because visitor numbers are lower than over the baking summer months though remember that you'll experience cold nights in June and July. Winter also the best time to travel to the region for prime game viewing - Sun City lies next door to Pilanesberg National Park and is close to Madikwe Private Game Reserve, both offering Big 5 safaris and plenty of accommodation.
Africa Safari Expert