Does a Green Sky Mean a Tornado? The Science Behind This Severe Weather Warning

March is Severe Weather Preparedness Month, and since we live in Indiana where severe weather and tornadoes are frequent this time of year, I've been working on a number of weather-related resources.

For as long as I can remember, I have heard that a "green sky means a tornado," but does it really? And also, why exactly does the sky turn green, anyway? I thought we'd take a little deep dive into what the science has to say.

The Color of the Sky Is All In The Eye of the Beholder

According to Scott Bachmeier, a research meteorologist at the Cooperative Institute for Meteorological Satellite Studies at UW–Madison, light is scattered by the particles in the air. During the daytime, violet and blue light is scattered, and since human eyes are better at perceiving blue light, the sky looks blue. Renowned astrophysicist Neil deGrasse Tyson shares more about why the sky looks blue in the video below.

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Why Does the Sky Turn Green During a Storm?

Thunderstorms often occur later in the day, as the sun is nearing the horizon. Sunset creates a red cast to the sky. However, thanks to moisture inside the clouds, the light underneath a massive thundercloud primarily appears blue. Bachmeier points out that when blue objects are lit with red light, the human brain perceives them to be green. The folks over at WCNC explain further that the closer you are to the storm, the more likely it is that the sky will appear green.

Does a Green Sky Mean a Tornado?

So does a green sky mean that a tornado is coming? Bachmeier says that while it can indicate that a tornado is possible, it does not mean there will for certain be a tornado.

You can check out a detailed explaination below in the video featuring tornado hunter, Ricky Forbes.

[SOURCE: University of Wisconsin-Madison; WCNC]