Earlier this week a derecho rolled across South Dakota, producing an eerie green skies.

Witnessing this phenomenon can be unnerving and ominous, such as what occurred Tuesday near Sioux Falls, S.D..

Fortunately there is a rather simple explanation for the color.

Like any colors of the sky it is all thanks to the sun. Since most severe storms appear in the afternoon, with energy from the sun building through the day, the sun itself is often descending towards the horizon.

As the sun sets the colors produced tend to darken, so while typically sunlight hits rainfall to create blue light there is a slight change.

The darker sunlight is often closer to red, when red light hits blue light reflected from the rain, it creates the green skies seen in South Dakota.

You may have encountered the weather myth that a green sky indicates a tornado. This is not true.

Although a green sky often appears during severe weather there is no direct correlation with tornadoes.