How does fog dissipate?

Answer

When temperature increases and humidity of air decreases the fog dissipates.

Answer,

Fog is moisture in the air condensing due to cooler ambient temperature at ground level. As the ambient temperature increases, generally due to the sun, the moisture in the fog will burn off and the fog will lift.

You can't see vapor, but you can see droplets of water, droplets small enough to float in air (brownian motion). Whenever the droplets evaporate (heat, low humidity, etc) the water doesn't go anywhere but now you can see through it, thus "no fog".