I’ve been in Cape Town a couple of times and every time I’d like to come back again. Cape Town has an hot summer between December and March and a cold and rainy winter from July to September/October. The best time for me to visit the city it’s in November or from January to late April, but it depends what kind of holiday you want.
If you want a relaxing holiday on the beach, the best time is between December and February. During this time the beaches are really busy and you’ll find a vibrant nightlife and beautiful sunny days. Unfortunately during December and January in Cape Town’s fierce south-easter wind blows strongly during this time, occasionally clearing the beaches and blanketing Table Mountain in cloud. During February the wind calms down and it’s much better!
April is absolutely fantastic (also for the better prices), uncrowded beaches and much less wind. If you like hiking I suggest you to go from late April to early June when days are crisp and clear, great weather for hiking… Otherwise if you want an adventure trip it’s better between late June to August to have a wonderful safari.