Gauteng residents have been warned to prepare for temperatures of up to 36 degrees, as a heatwave grips the province this week.
Parts of the Free State, Eastern Cape and Northern Cape will also see a sharp rise in the mercury over the course of the week.
Prieska and Augrabies Falls in the Northern Cape will see maximum temperatures of up to 42 degrees on Monday.
The South African Weather Service has warned of possible veld fires over the interior.
READ: Western Cape set to cook as temperatures top 30 degrees
Forecaster Lulama Pheme says the service has issued advisories for people living in central parts of the Free State, the central Karoo, the central Garden Route, central parts of the Eastern Cape and the Northern Cape.
Pheme says there is a "30%" chance of rain over the eastern parts of Mpumalanga later in the day.