We've all had that dreaded moment.... It's summer time, and your car has been baking in Mojave-like parking lot for hours. And now you need to get inside that oven and get on the road. So how do you cool it off? Get in and boost the air conditioning? That can take a while... Try this:
1. Open the car, and roll down the window on the passenger-side. If you have a four-door vehicle, roll down both windows on the passenger side.
2. Cruise back to the driver-side, and open the door. Now close the door. Now open it again. Basically open and close several times. This is causing the air to circulate inside the vehicle.
3. After looking like a crazy person with all the opening and closing, get inside and gauge the temperature. All that opening and closing should have forced enough hot air out to drop the temperature by a wide margin. If all else fails, you can always use the air conditioner and suffer through a Sahara-esque five minutes until it cools down!
Source: http://consumerist.com/2011/07/22/cool-your-car-down-quickly-with-this-trick/