Fog, dew, and clouds are all related. In fact, just one change in the conditions—such as the presence or absence of air currents—could make the difference as to whether there will be fog, dew, or clouds. Let’s see why this is so, and why fogs appear in certain places.

Fog particles are small, less than 0.001 millimeters in diameter. When you have a dense fog and can’t see in front of you, it’s because there may be as many as 1,227 of these particles in one cubic centimeter.