The SA Weather Service in Port Elizabeth says the official maximum temperature of 46.6 degrees Celsius for Addo Elephant Park on Monday was an all-time record, since measurements started in 2005.
Spokesperson, Garth Sampson says the previous record was 45.8 degrees measured on 9 February 2010.
He says the mercury rose to the staggering level at 15h35 on Monday afternoon, at which point the Heat Danger Index was at 124.
Sampson says the apparent temperature was 51 degrees Celcius.
Apparent temperature is the general term for the perceived outdoor temperature, caused by the combined effects of air temperature, relative humidity and wind speed.
The heat index and humidex measure the effect of humidity on the perception of temperature.