When you’re in the mountains and see a thin cloud hanging over the valley, you might assume it’s fog. Or maybe it’s mist, or smog. What do these words mean? It all depends on how they were formed—and where they came from! Here’s a quick guide to the differences between these types of clouds:

Mist originates from water droplets getting into the air.

Mist is a cloud that has a diameter of less than 2 millimeters. It’s formed when water vapor condenses into tiny droplets and is suspended in the air. Mist can form almost anywhere, but it often occurs over bodies of water as warm air passes over cooler bodies of water and evaporates some of their moisture. When this happens repeatedly, you get fog! Fog is just mist that’s low enough to be able to see your feet or less if you stand still for too long.

Smog is thick fog that contains pollutants from cars and factories (like sulfur dioxide). It can cause serious health problems if someone breathes it in long enough without protection because these pollutants are harmful to humans when they’re breathed in directly through your lungs.*

Fog is a low-lying stratus cloud.

Fog is a cloud that is near the ground. Fog is made up of water droplets suspended in the air. This means that fog isn’t actually a cloud, it’s just a layer of air where there are many water droplets floating about. Fog usually forms when there’s relatively warm air close to the ground, and cold air above it—this causes the moist air to cool down and some of its moisture condenses into tiny liquid drops. Fog can also form when humid air moves over a cold surface (like at night over an open body of water). Fog often has a greyish-white appearance because light rays bounce off these tiny liquid particles before they reach your eye to be seen as an object; this process is called scattering*.

Smog is a result of human activity.

Smog is a type of air pollution that occurs when sunlight reacts with chemicals released by cars, factories, and other sources. The main cause of smog is nitrogen oxides (NOx). When these react with volatile organic compounds (VOCs) such as methane and benzene in the presence of sunlight, they form ozone and other harmful pollutants.

Smog can be especially bad in cities where there’s a lot of traffic or industrial activity—and it can linger for days after the pollution source clears out. Because smog is caused by human activity rather than nature itself, you might think it would be easy to avoid: just stay inside on bad air days instead! However, most people have no choice but to go outside every day for their jobs or errands; so avoiding smog isn’t always an option unless one lives far away from any large cities or industrial centers.

Haze consists of fine dust and smoke in the air.

Haze is the result of light scattering by fine particles in the air. It’s a global problem that occurs in urban and rural areas, as well as regions with high-altitude mountain ranges.

In urban areas, haze is caused by pollution and dust. In rural areas, it can be caused by wildfires or agricultural burning. In both cases, humans have an impact on this type of atmospheric condition because we are responsible for these types of activities that produce particulates like smoke from fires or dust from farming operations.