Good question. Well, because human beings have basically screwed the planet up the seasons in the Cape (and everywhere else) are not as predictable as they used to be but here is a good guide.
Summer – December to February
Autumn ( Fall if you’re American) March to May
Winter (All year is you’re British) June to August
Spring September to November
We are in Winter now, in the Western Cape (Cape Town) it gets cold and windy. The wind hits the Peninsula HARD from the South East, comes straight off the Ocean and hands you your ass. Add driving rain to the mix and Winter in the Cape can be tough. Bring warm winter clothes and waterproof clothing. This morning it was cold, wet and windy and now it’s sunny and I am warm so you need to bring a mix of clothing.
Tidal pool at St.James. Great if you don’t want to drown
During summer in Cape Town the temp averages around the 27 C Mark. Because I am bald, white Englishman, I can overheat during a Luna Eclipse so Summer is hard going for me. I always have long sleeved cotton shirts and hats. I don’t use sun screen myself because I don’t like putting chemicals onto my skin or into my body but that’s not medical advice, I am not telling you not to bring sunscreen. You do what you like, I don’t give a shit.
So in summer you need summer clothes BUT still bring jumpers (sweaters) or wind breakers as the wind is relentless when it comes and can come all year. in Winter bring waterproof clothes and summer clothes
You can bring swimwear with you as well as there are nice tidal pools along the coast you can swim in. You can swim in the open sea if you like but be warned. The water is cold and your testicles will become the size of pin heads and your penis will retract back into your body immediately. Also your nipples will fall off.
So that is it really. here is a useful link to help you out because I am bored talking about the weather now. https://www.holiday-weather.com/cape_town/averages/
The same rules apply to the Garden Route, bring the same clothing. By the way, if you’re coming to South Africa and your thinking about experiencing the Garden Route then do it with Cape Convoy (if you don’t then you’re crazy) and I will throw in a FREE full day Cape Point tour for you https://capeconvoy.co.za/garden.html
Professor So from Singapore experiencing the South Easter in the Cape