Well, I guess I was right, unfortunately. Driving back home, and passing Graaf Reinet, the temperature steadily climbed. By the time it reached 35.5 degrees Celsius, surprise! My car broke down, again, for the 3rd time. Ai jai jai! Feels like déjà vu! So I managed to barely make Gariep while the temperature climbed to 39.5 c*
I reckon that if I wait until dark, the conditions will be more suitable, for the car at least. Night driving long distances is never fun, and if the car breaks down then, it's even worse. But I have no other option than to take the gamble.