We went in December, it was very nice and sunny. 70s and 80s. December is our beginning to winter ( we live in western NY) December in Cape Town is late spring. It only rained one evening when we were there. Remember that Cape Towns climate will be like Texas or the Carolinas. South Africa does have two ski areas in the mtns. They are open from mid June to end of August. I would think any time would be nice to go. Mike K has been there but I don't know what time of year he went.
www.sailhoneycat.com
Greg