The greenhouse effect is behind the hot temperatures in your car.
Visible light from the sun enters your car through its windows and is absorbed by your car’s interior in the form of heat. Not all light, however, can get through the glass molecules in your windows.
Infrared waves, which are longer than visible light waves, are mostly blocked from entering your car’s interior through the glass. This is actually the key to why your car heats up so much when you park it in the sun on a hot day.
Though most infrared rays can’t get into your car through the windows, the materials in your car’s interior — the dashboard, the seats, the carpet, etc. — actually radiate infrared rays as a way to release the energy they absorb from visible light.
For the same reason infrared rays struggle to get into your car through the windows, the ones created inside your car also have a hard time getting out. Rather, they bounce around inside, heating up your car’s interior.
On a hot, sunny day, your car’s interior could quickly reach over 150 degrees. In fact, cars can get so toasty that the Weather Network was able to bake cookies on a dashboard.
Window film can help dramatically reduce the heat in your vehicle by rejecting up to 60% of visible light. Even with window film or a sun visor, however, it’s important never to leave passengers or animals in the car for longer than a couple minutes without the AC running.