Car Temperature Profile

Ever wonder why when you open your car door on a hot day you feel a stream of hot air coming out?  Is it currents introduced by opening the car door, or simply the fact that the air in your car has expanded because of the heat and has a higher pressure as the volume stayed the same?  These are the questions that I should be doing my thesis on!  Well, we measured the temperature profile with a thermocouple of Timmy's car during pickup, starting around 2:30 ish and going to 5 ish. It was sunny outside the entire time, but at some point the car became shaded. So the car heats up pretty quickly, but then seems to reach a thermal equilibrium which either declines because of the shading / outside temperature decline.