I certainly can't remember that we had these kinds of storms when I grew up in Cape Town. Thunderstorms were an occasional event in December and then only towards the north of Durbanville. Certainly no over Table Mountain and Kloofnek.
I must say that the weather in Cape Town is certainly changing probably due to global warming. I see that the Cape Town region has been identified as a hot bed of change due to global warming. Doesn't sound too good for the delicate eco system the Cape is so known for.