Being in the Southern Hemisphere means that South Africa has reverse seasons to the UK:

Spring is from September-November

Summer is from December-February

Autumn is from March-May

Winter is from June-August

South Africa is a year-round destination, with average day temperatures in summer ranging from a minimum of 15°C (59F) to a maximum of 28°C (82F). In winter the average day temperatures are 19°C to 23°C (66F to 73F).

Spring – Warm days and very little rain will fall over this period (ave. min 15° max 28°)

Summer – Hot sunny days and lovely warm evenings (ave. min 20° max 30°)

Autumn – Warm days and very little rain will fall over this period (ave. min 19° max 28°)

Winter – Warm, sunny days but cooler evenings (ave. min 9° max 23°)

Rainfall really does depend on the region your clients are in. The Mediterranean climate of the Western Cape means it tends to get its main rainfall during the winter months, whereas the tropical climate of KwaZulu-Natal means it gets its rainfall through the summer months.