NASHVILLE, Tenn. (WKRN) — Most people want to know what the UV Index (UVI) is when going outside during the summer—but what is it?

UVI is the amount of ultraviolet radiation your skin will be exposed to outdoors at solar noon. Solar noon is when the sun is at its highest point above Earth and occurs from 11:30 a.m. to noon.

UV Index concern is typically highest during the summer because that is usually when it’s at its peak. During the summer months, the sun’s rays must travel through less atmosphere to reach the surface.

In addition to cloud cover and elevation, the UVI also accounts for how much of the ozone hangs over us in the stratosphere.

The levels vary depending on where you are, but they are at zero overnight and can reach up to 16 at high elevation in the tropics.

This weekend the UV Index will reach 8 in Nashville on Saturday and Sunday. During the hours between 10 a.m. to 4 p.m., you should limit your outside time.