A Green Sky....Does It Mean A Tornado Is Coming?

Ms. Shaw and her Earth Science students at Southeast Polk Junior H.S. in Runnells, Iowa have asked me if when the sky turns green, does that mean a tornado will form or is coming?


It is well known that often times the sky turns a hue of green before severe weather strikes. The thing is, this doesn't happen ALL the time, thus there is no rule of thumb with this strange phenomenon. However, if I saw a green sky, it would mean to me that I should turn on the TV/radio and find out what's going on in my area.

My Story:

In fact...I have seen the green sky before and it did warn me of severe weather.

Back when I was in the very lucrative pizza delivery business and thus living at home...I saw this green sky from my window. I went to turn on the TV to figure out what was going on, and before I could get to the TV, the tornado sirens sounded.

My dad and Grandma were sleeping...so I woke them up and my family and I went down to the basement. The storm was likely straight line winds, not a tornado, and destroyed our patio and took off numerous tree limbs damaging our roof in the process. I knew something was up by the look of that greenish sky, as I had heard about such reports from storm spotters.


So Why Does the Sky Turn Green?

No one knows exactly, but here's one idea...

Sunlight is comprised of many different colors. The colors that comprise sunlight get absorbed, reflected and scattered as they encounter the particles in our atmosphere (like Nitrogen, Oxygen, dust, etc...)

For example, our sky is blue because the blue color in sunlight is scattered by particles in our air. When this blue color scatters in all directions, it may eventually hit your eyes, and voila! You see a blue sky. (Click Here for more on the whol blue sky deal)

This type of optical phenomenon is suspected to be the reasoning behind the green sky effect. Exactly why the green hue appears is not exactly known, but the tremendous amount of water vapor may be the culprit.

It is hypothesized that the water vapor makes the clouds look blue. But when the sun is at a low angle, like at sunset or sunrise, the blue is scattered out of light. This may allow the color green to show up more vividly.          


Here is a picture at left of a cool tornado, with a reddish sky as the sun sets. Perhaps the green sky effect occurs due to the same reason that our sunset/sunrise sky appears reddish. That is to say that the green is a result of the scattering out of blue to the point that the green tint of light can be dominant.

However, the green sky is still a mystery.






More Savviness exists on the blue sky/red sunset topic at

Just Click Here

Thanks to the kids at Southeast Polk Junior High in Runnells, Iowa for their great question.

If you have a weather conundrum too,

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