The South African Weather Service (Saws) has warned of severe thunderstorms for KwaZulu-Natal, the Free State, the Northern Cape, and the North West.
Saws said this could lead to localised damage to infrastructure and settlements.
"A Yellow Level 4 warning of severe thunderstorms with heavy downpours and strong winds are expected over parts of KZN, except the extreme northern parts," Saws said.
The forecaster added that a Yellow Level 2 warning has been issued for possible strong winds, large amounts of small hail, and heavy downpours over the south-eastern parts of the Northern Cape, the south-western parts of the North West, the western parts of the Free State, and the eastern parts of the Eastern Cape.
The N3 Toll Concession has appealed to road users to exercise extra caution and patience under these conditions.
"Please drive defensively, switch headlights on, increase following distances, and slow down. Speed limits are set for ideal road conditions, not for poor weather and difficult driving conditions," the N3TC's Thania Dhoogra said.
She urged motorists to be prepared and plan ahead.
The adverse weather conditions are forecast over both KZN and the Free State, and Dhoogra has urged drivers to report problems or get emergency assistance.