WET, WET, WET: A rain drop creates a crown of water as it hits a puddle during a heavy thunderstorm in Johannesburg yesterday Picture: HALDEN KROG

"Lightning is the biggest killer in summer," said South African Weather Service forecaster Evert Scholtz.

He described the thunderstorms that have lashed Gauteng since Friday, including a hail storm in Johannesburg yesterday afternoon, as common during summer. But he could not say the same for the flooding and cold in Western Cape and Northern Cape.

"It is not normal for it to be so cold during this time of the year. The maximum has been 12C, and that is cold in summer," Scholtz said.

Cape Town disaster risk and management centre spokeswoman Charlotte Powell said residents from Cape Flats, Mandela Park, Khayelitsha and parts of Philippi had called for help.

In KwaZulu-Natal, the department of local government and traditional affairs yesterday erected tents to house 178 families displaced when their homes were hit by a "mini tornado" on Friday.

"Tornados are not uncommon in KwaZulu-Natal, Free State and Transkei at this time of year," Scholtz said.