Hi Carole
Just to add my 2p worth! I went to South Africa (Travelsphere) with the add on early last September. I was anticipating warm weather getting hotter as we travelled north. That was one of the reasons for choosing the earlier date. In the end it was quite cool in Cape Town with a drizzly day and too early to enjoy the best of the gardens we visited.
The weather remained comfortable as we journeyed up country - it actually snowed in Johannesburg :huh: - but I understand that was most unusual! By the time we reached Zambia it was very hot (sorry - don't have degrees) but I managed to enjoy everything comfortably and I do not like very hot weather. I don't remember it being humid but most of Southern Africa was in the grips of a drought.
With hindsight I would perhaps choose a later September/early October date - but nothing is certain with the weather that's for sure!
It was a wonderful holiday (I did the whale watching tour) - a great way to see a lot of South Africa in one holiday.