What do you think water droplets formed on the outside of the car window.?

When u drive for long destinies and have the a/c on and its hot outside so t happens when you stop your car after having driven for a while in the sun. If you stop for a few minutes (going for a few items at the supermarket), you will see it when you return to the car. It disappear if you are driving or if you stay parked long enough for the air inside the car to get warmer.

The water droplets depend on the level of humidity, if it is high enough it will form droplets.