MEMPHIS, Tenn. (WMC) - Fog and clouds may look similar, but they are actually considered two different things based on where they form.
Similar to clouds, fog forms when water condenses into the air. This is achieved by either an increase in moisture or cooling the air to turn water vapor into liquid. With more moisture on the ground (like after rain), fog will be more likely to form. Also, sometimes the liquid water will turn to ice if it’s cold enough. This is called ice fog and is common in Alaska.
However, fog only forms at the surface. If it forms above the surface, it will be considered a cloud and not fog. In fact, fog is most common on clear nights with NO clouds in the sky.
Clouds form at many different altitudes and can be several miles above the surface. So, the only real difference between clouds and fog is the altitude. Typically, if it’s lower than 50 feet, it is considered fog. If it’s higher than 50 feet, it is considered a cloud.