South Africa will move to lockdown alert Level 2 from Monday.
President Cyril Ramaphosa said COVID-19 infections continue to rise sharply.
Over the last seven days, there has been an average of 3,745 daily new infections.
“This is an increase of 31 percent on the previous week and an increase of 66 percent on the week before that,” Ramaphosa said in an address to the nation.
“The proportion of COVID-19 tests that are positive has more than doubled in the last month from around 4 percent to more than 11 percent, even as we have increased testing across the country.
“We are advised that a positivity rate of over 5 percent is a cause for concern.”
Ramaphosa said the Free State, Northern Cape, North West and Gauteng have reached the threshold of a third wave of infections.
“It may only be a matter of time before the country as a whole will have entered a third wave,” the president said.
“According to our health experts, the recent surge in new infections is due to the increasing number of social gatherings where people are not observing essential health protocols.”