South Africa weather is famous for its sunshine. It's a relatively dry country, with an average annual rainfall of about 464mm (compared to a world average of about 860mm).
At the same time, temperatures in South Africa tend to be lower than in other countries at similar latitutes - such as Australia - due mainly to greater elevation above sea level.
The FIFA World Cup will be in the South Africa winter. And the winter in South Africa (May to July) is characterised in the higher-lying areas of the interior plateau by dry, sunny, crisp days and cold nights.
So it's a good idea to bring warm clothes.
To check the South Africa weather in real time I recommend looking in the
South Africa Weather Service website.