I have a friend that is always so argumentative that I want to shut him down for once. How is it that a car in temperatures mildly above freezing say 34-37 above freezing can frost over before reaching the freezing point. Also does thermal conductivity of the metals, glass, paints, and plastics affect this outcome or is it mainly due to evaporation of dew on the vehicle? Or is there something else that is creating this outcome. Or could this be an inaccurate temperature reading.
The interior of the car is radiating to space through the windows. This drops the interior temperature of the car below the air temperature until an equilibrium is reached. At equilibrium, the energy flux entering the car due to convection with the air is equal to the energy flux into space. The temperature of the windows will be between the interior temperature and the outside temperature.
The frost will only occur on clear nights, because the effective temperature of space is much less than the temperature of clouds. You could prevent the frost by lowering the windows, thereby increasing the energy flux into the car by the air.