the air that is supposed to cool the fluid or the coolant that flows through the radiator is not cool enough to do the job, hence overheating can happen
The radiator is where air flows to cool the fluid. If the air that flows in is also warm, then the cooling system does not work as well.
B the radiator automatically shuts off when the outside temperature is too high
C with direct sunlight, the cooling system does not work
D hot days have the tendency to melt the radiator