Buzz
In tornado-prone areas of the U.S., a popular piece of folklore suggests that a greenish sky is a sign to take cover. But what causes tornadoes to bring about this unusual green tint in the sky? According to SciShow’s Michael Aranda, it all comes down to how water droplets interact with light, reflecting different colors in the spectrum.
Normally, the sky looks blue because the shorter, bluer wavelengths of light scatter more easily off air molecules than the longer, redder wavelengths. However, when the sun sets (or rises) and when storms develop, sunlight has to travel through more air, increasing the number of water droplets in the atmosphere.
As tornadoes form later in the day, particularly around sunset, they reflect green light—often hidden during typical sunsets—due to the water droplets in the clouds, which send green light toward our eyes. This doesn’t always mean a tornado is imminent—it could just signal a heavy storm. Still, seeking shelter is likely a wise move.
To learn more about how water and light work together to create the green sky effect before a storm, watch the full SciShow video below.
