COLUMBIA, South Carolina — Earth's surface radiates heat back into space, leading to cooling. This cooling, along with moist air, creates ideal fog conditions.
Fog emerges when the air at the surface cools to the dew point, the temperature at which water vapor condenses into droplets.
A strong breeze will usually mix the air at the surface, preventing fog, but calm winds, or no wind at all, allow for the gradual cooling needed for fog to develop.