Best time to go to Africa?

Hi all,

I'm thinking of incorporating about 6 weeks of volunteer work into my travels next year, and it'll probably be in either South Africa, Tanzania or Kenya.

I'll be able to do this anywhere within late August to December-ish, but I'm unsure of which times would be best weather-wise. I'm really not into hot weather at all, let alone hot African weather, so the later months are obviously out, and cold weather/rain would be undesirable.

So what about August/September? Is it still pretty cold then, or does Africa warm up faster than Australia?

I have absolutely no idea about weather patterns in Africa, obviously. Thanks for the help, if you can!