KNOXVILLE, Tenn. (WATE) — Fog is a common occurrence in East Tennessee, in fact, from the Cumberland Plateau to Knoxville, there is an average of 30 to 40 days of dense fog per year and Johnson City and Asheville, North Carolina, see about 40 days per year.

There are many types of fog including steam fog. You can find steam fog above bodies of water, like lakes or rivers. It often looks like a cloud of steam rising from the water. It is most often seen in the fall or heading into winter.

Steam fog forms where a cold air mass moves over a warmer lake or smaller body of water. Once this happens, the water will slowly evaporate and add moisture to the air right about the surface. The air above the surface will be warmed by the water below. As the moisture rises, the water turns into vapor, which looks like steam. This creates is steam fog.

It’s kind of like you were boiling water on a stove, rising that warmer air into cooler air and you get steam or steam fog.