What’s the difference between fog and mist?

For many of us terms “fog” and “mist” tend to mean the same – a milky-white low-lying cloud. We all know that we must be extra careful when driving in those conditions, use fog lights and never ever exceed the speed limit. But we rarely care if the cloud around us is a mist or a fog. Almost like it’s the same thing. However, those words are not so interchangeable as we may think.

What fog and mist have in common?

On the surface, mist and fog seem like they are the same thing. They both are an atmospheric phenomenon, created when tiny water droplets get suspended in the air in a cloud form. They both form close to the ground and have milky white or slightly gray color. In both cases, a very high humidity (around 95%) is necessary in order for a fog or mist to form. Both are also pretty good at restricting the visibility.

So what’s the difference between fog and mist?

Although subtle, there’re quite a few differences between those two; they may not matter in our daily life, but are very important for aviation and maritime safety. First of all, fog is much denser than a mist. Because of this, fog reduces visibility greater than a mist: it is possible to see out to about 1-2 km (1.2 miles) in mist, but in a fog to under 1 km (0.6 miles). Because of its greater density, fog also tends to last longer, while mist disappears in a short period of time. Of course, other factors, like wind, raising the temperature or changes relative humidity, can affect how long a for or a mist will last.