A window assembly for a vehicle includes a glass window panel and a display device disposed at an interior surface of the glass window panel. The display device is operable to backlight or illuminate at least one icon or alphanumeric character. With the window assembly mounted at a vehicle, and when the at least one icon or alphanumeric character is backlit or illuminated, the at least one icon or alphanumeric character is viewable through the glass window panel by a person exterior the vehicle. With the window assembly mounted at a vehicle, the display device is activated to display an icon responsive to determination that an in-cabin temperature of the vehicle is above a threshold level.