As mentioned, there are many potential causes. This is a short list of some possible reasons.
Car’s a/c system not cold?
Car ac not blowing cold air. Turn the air conditioning on while the car is running. The air is blowing from the vents and it is cool air, not hot air, but its not blowing enough cold air to lower the temperature inside the car. Having your car’s air conditioning go out suddenly can ruin your day fast.