Respuesta :
This is because air is trapped inside the car and it heats up to the same temperature of the car. Think of the car as a greenhouse.
Explanation:
On a sunny day, when we leave car out side with doors closed and windows up, the temperature is greater inside the car than outside. This is because the radiations from the Sun gets trapped inside the car and does not reflect back. The air inside the car gets heated up from this radiation. Since, air cannot escape the inside of the car as it is closed, the temperature rises eventually making the inside of the car hotter than the outside.