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Fast Fact: Fog

Have you ever woken up on a foggy morning and wondered where all that fog came from or even what fog is? Essentially, fog is a cloud touching the ground. Just like clouds, fog consists of tiny water droplets hanging in the air.

There are many different kinds of fog. The type we most often experience in Illinois is called radiation fog, or ground fog. It usually develops in the evening, when heat absorbed by the ground during the day is released back into the air. When it’s cold, we also sometimes experience freezing fog or ice fog. There’s also something called super fog, which forms when water vapor combines with smoke from wildfires. We don’t experience super fog here in Illinois because wildfires aren’t common here. This is the thickest kind of fog, and it can make it hard to see your hand in front of your face. Some places are known for fog. In places like San Francisco, fog is common because the cold air over the ocean moves over warmer land, causing fog to form.


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