In Southern Africa summer is from October to April and winter is from May to August. Summers tend to be hot, with temperatures around 30°C (86°F), and therefore is the preferred time to go on beach holidays, such as in Mozambique. Winter temperatures during the day are around 15°C (59°F) and fall to as low as -10°C (32°F) overnight. It can be extremely chilly on early morning or evening safari drives so it is advisable to pack some warm clothing for your trip!
East Africa (namely, Tanzania) enjoys warm weather year round with an average daytime temperature of 70°F. You may need a sweater at night and in the early morning.