Why does a glass of ice water eventually have water droplets on the outside of the glass?

Warmer water inside the glass moves away from the ice and to the outside of the glass.
As the ice melts, the pressure inside the glass increases, and some of the water is pushed through the glass.
Liquid water droplets in the air are attracted to the cold glass.
Water vapor in the air comes into contact with the cold glass, losing energy to it and condensing into droplets.