When I lived in one of the hottest cities in the country--Phoenix, Arizona--I learned a technique that will cool down the interior of a hot car quickly.
On a hot summer day, the temperature inside a parked car can easily reach 130 degrees. Many of would get into the car, turn on the ignition, and lower the driver's window. Then we slowly turn on the AC until the air from the vents turns cold. Then, we would crank it and wait for the interior to cool down.
As you see in this video above, there is a much quicker way to cool down your car.