I wouldn't consider this question either simple or quick.
If he lives in Texas (or somewhere similar), and the car is sitting in the sun all day, the temperatures inside the car can reach over 180 degrees (farenheit). That's HOOOOOOOTTTTT!!!!! by anybody's standards.Hot enough to cook meat anyway. And that's just the air temperature. Surface temperatures of surfaces in direct sunlight can go over 240. So his question about heat is entirely relevant.