I enjoy when creative people develop their ideas and bring them to the world.
Even thought my Golden Retriever loved to feel the wind in her face from the car window, I was well aware of the dangers, not to mention being disgusted by the drool along the windows that I had to clean up.
Sue Stipanovich figured out how to create a screen for car windows, BreezeGuard. It is a powder-coated steel screen with half-inch openings that keeps pets safely inside the car while allowing for a cool breezes on warm days.
Sue made one for her own car, but interest from others prompted her to make them for sale. She and her husband, Tony, hand make each one specifically to fit the model of your car. They install from the inside to allow for free movement of the window glass.
Remember, if it is too hot outside for you, it is too hot for your pet in the car regardless of having a screen.