South Africa is at the height of summer, the Western Cape is at its best, the east side can be a bit too hot, and very humid, especially in KwaZulu Natal. Botswana is in its green season, very good for birders, there is still plenty of game to be seen, but expect some showers or sudden storms.
It’s the dry season in East Africa, peak season for migration in Tanzania – you will need to book early to see this. Kenya offers good game viewing throughout the year.
January is dry and hot in Sierra Leone. It’s peak season for winter sun in Oman.
Be careful of the Seychelles, which can be wet, though these tend to be short sharp downpours rather than continuous rain; Mozambique and Mauritius can also be wet.
It’s cyclone season in Madagascar. Namibia is very hot at this time with temperatures over 35°. Zambia is very wet and roads often impassable, though this will not affect Victoria Falls.