Yes SA is a big country and the climate is not the same everywhere that is for sure.
Generally speaking, the whole country other than the Western Cape region, has dry winters and wetter summers.
The Western Cape has dry, hot Mediterranean summers and wet cool winters while the rest of the country has dry cool winters and warm wetter summers
Joburg is 5000-6000ft above sea level so never humid, has cool evenings and cold winter nights and bright sunny winter days. Maybe the best climate on the planet ...there are other issues though.
Limpopo has dry cool winters (warmer than Joburg as it is lower) and hot summers with thunderstorms.
Mpumalanga has warmer dry winters (lower again than Limpopo) and hotter and wetter summers.
KZN is like Mpumalanga at the coast but in the midlands it is more like Joburg.
Karoo and Northern Cape is very dry (a bit wetter in summer) and can get cold nights in winter.
If i had to choose and had no obligations I would spend:
- May at the beach in northern KZN or Mozambique (fishing and surfing and diving),
- June, July, August in Mpumalanga, Limpopo and Karoo and Northern Cape (and Zim) Hunting,
- September in Mozambique fishing,
- October, November in the Southern Cape playing golf and chasing Guineafowl
- and December -April in CT enjoying the magnificent weather, great wine, fishing for tuna, surfing and preparing for next year
It's pretty much the most beautiful country ive been too having visited about 75 countries around the world. Diversity, weather, opportunity and ease of getting around. Im a little biased of course