The cut-off low pressure system that resulted in parts of South Africa being hit by heavy rains and floods is now weakening, said the SA Weather Service.

However, a warning of severe thunderstorms - with heavy downpours and large amounts of small hail - was issued for Johannesburg on Thursday.

"The intense storm has just passed south of Johannesburg. It is now currently more over Ekurhuleni and will produce heavy downpours and flooding on the roads," forecaster Dipuo Tawana said.

Tawana said the thunderstorms were now in Johannesburg West.

KwaZulu-Natal was hit by the heavy rains at the start of the week, while the Eastern Cape town of Port St Johns reported that low-lying areas had been flooded by heavy downpours. 

Tawana said the cut-off low pressure system was the main cause of the rains that left hundreds displaced and scores dead. 

Earlier on Thursday, News24 reported that the death toll from heavy floods in KwaZulu-Natal had risen to 70, according to Premier Sihle Zikalala.

"The cut-off low system is currently weakening and exiting the country. We are expecting [it] to completely exit by this evening," she said. 

Mpumalanga, Limpopo and north-eastern parts of KwaZulu-Natal could still expect isolated showers and thundershowers on Friday, said Tawana. 

She said fog was also expected on Saturday morning in Mpumalanga and Limpopo. 

"Otherwise the system is clearing and from the weekend things should be fine," she added. 

Motorists have been advised to continue driving with caution.

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