On Thursday, Johannesburg reached 32°C, while the mercury rose to 35°C in Pretoria, said the SA Weather Services (Saws). Both cities have zero chance of rainfall on Thursday and a 30% chance on Friday.
Johannesburg and Pretoria's maximum temperatures on Friday will be 34°C and 35°C.
The temperature in Johannesburg will reach 33°C on Saturday, while the maximum in Pretoria will be 35°C.
Saws forecaster Mbavhi Maliage said no rain is expected in Limpopo and Mpumalanga on Friday, while light thunderstorms are expected in Gauteng, the Eastern Cape, Northern Cape and the eastern parts of the Free State from the afternoon into the evening.
Maliage said the heatwave will continue, despite the thunderstorms.