Don’t be fooled by thinking because you are in Africa you are guaranteed year round weather. Cape Town along with the rest of the Western Cape definitely has summer and winter.
Summer can be hot and dry with temperatures in January and February regularly into high 20s and upwards. You can generally expect pretty consistent summer weather from December to through into April. There is however a chance of the famous “Cape Doctor” a strong South Easterly wind that comes in from the sea and although it brings some respite from the hot weather there can be some strong gusts.
May/June and Oct/Nov are less predictable as the fall between the main seasons. It can be a great time to travel as it less busy, sometimes cheaper and there is chance you could still get perfect weather.
July-September is classified as winter. It is generally cooler, perhaps down to 8 or 9 degrees, so not cold by UK standards but this is when Cape Town expects to receive the majority of it’s rainfall, vital to fill the dams that are virtually drained over summer.
There are still advantages to winter travel, some days can still be fine and its flower season around August/September on the West Coast, and definitely the best time for Whales. If you get a cold rainy day, there are plenty of vineyards where you can cosy up in front of a log fire and enjoy a wonderful glass of local red wine.