The sky can take on a greenish color during a tornado due to the light scattering effect of debris and water droplets suspended in the air. Here’s a quick overview of why this happens:
Light Scattering
Sunlight is made up of a spectrum of colors. The shorter wavelength blue and violet light scatters more easily than longer wavelength red and orange light. Under normal conditions, the blue light scatters throughout the atmosphere giving the sky its familiar blue hue.
During a tornado, debris like dust and dirt particles get whipped up into the air. The increase in airborne particulates causes even more scattering of the short wavelength green light, making the sky appear greenish.
Water Droplets
Tornadoes are associated with severe thunderstorms which produce a lot of moisture. Water droplets from the storm also get suspended in the tornado funnel. The water droplets cause additional scattering of green light, adding to the green coloration.
Complementary Colors
Another factor that can contribute is the contrast between complementary colors. The red soil and vegetation common across Tornado Alley provide a red-colored background. The green sky appears even more vivid and pronounced when viewed against this crimson backdrop.
When Does a Green Sky Happen?
A green tinted sky is most likely to occur right before or during a tornado when the spinning winds whip debris high into the air. Some key times when you may notice it:
- Just before a tornado touches down as the rotating winds pick up
- During the tornado as it draws dust and debris into its funnel
- Right after a tornado as debris remains suspended
The green coloration is typically gone shortly after the tornado passes when the debris gets re-settled to the ground.
How Common is a Green Sky?
While a green sky is strongly associated with tornadoes, especially in Tornado Alley, it is not guaranteed to happen. Here are some stats on frequency:
- About 1/3 to 1/2 of all tornadoes have an associated green sky
- More common with stronger tornadoes like EF3 or higher
- More common with tornadoes occurring during late afternoon hours
- Happens more frequently across the Great Plains and Midwest
So while a green sky is not seen with every tornado, it is a common enough phenomenon during significant tornado events to be one clue to watch out for.
Other Color possibilities
While green is the most common color, some other hues can be observed as well:
- Yellow or brown – Due to large amounts of dust kicked up
- White or gray – When extremely heavy rain saturates the air
- Purple or pink – If red dust mixes with green light scattering
- Orange or red – From sunlight refracting through suspended droplets
So if you see any unusually colored skies, especially in an active storm, take it as a sign to be alert for a potential tornado!
What Should You Do if the Sky Turns Green?
Here are some tips if you observe a green tinted sky during a storm:
- Quickly get to a safe, reinforced shelter or lowest level of a sturdy building.
- Get away from windows or doors. Flying debris in a tornado causes most injuries.
- Listen for tornado warnings. A green sky means a tornado is very likely.
- Protect your head and stay low to the ground until the storm passes.
- Do not try to outrun a tornado in your car once it’s sighted.
Heeding warnings and seeking proper shelter when you spot a green sky can save your life!
The Takeaway
To summarize, the main points on why tornado skies turn green:
- Sunlight scattering effect increased by debris in the air
- Water droplets from severe thunderstorms add to light scattering
- Most likely right before, during, and after a tornado
- Greenest when tornado is at peak strength
- About 1/3 to 1/2 of tornadoes have some green sky
- Seek immediate shelter when you see it!
So next time storm skies start to take on a sickly green look, don’t waste time wondering why. Use it as a warning to take life-saving shelter from a potential tornado!
Frequently Asked Questions
What causes the green color in tornado skies?
Sunlight scattering through debris and water droplets suspended high in the air by the tornado’s winds. The green hue is caused by shorter wavelength blue and green light being scattered more than other colors.
How do I know if a tornado is coming by the color of the sky?
A greenish sky is one of the most well-known visual clues that a tornado may be imminent or occurring nearby. Take shelter immediately if you see an odd green color or tint to stormy skies.
Can a green sky happen without a tornado?
It’s rare, but possible. Dense blowing dust or extreme hail storms could potentially cause a greenish sky without an actual tornado. But it’s best to assume a tornado is occurring and take precautions.
What’s the difference between a green sky and green clouds?
A green sky affects the entire sky while green clouds refer to isolated darker green areas low in the sky. Both are signs of a possible impending tornado.
How long does the green color last during a tornado?
The greenish tint typically appears right before the tornado touches down, lasts while debris is lofted during the tornado, and lingers briefly after it passes before fading as debris drops.
Historical Green Sky Tornado Examples
Here are some notable historic tornado events where first-hand accounts described greenish sky coloration:
| Tornado | Date | Strength | Location |
|---|---|---|---|
| Tristate Tornado | March 18, 1925 | F5 | Missouri, Illinois, Indiana |
| Waco Tornado | May 11, 1953 | F5 | Waco, Texas |
| Flint Tornado | June 8, 1953 | F5 | Flint, Michigan |
| Bridge Creek-Moore Tornado | May 3, 1999 | F5 | Oklahoma City, Oklahoma |
| El Reno Tornado | May 31, 2013 | EF3 | El Reno, Oklahoma |
These major tornado events all occurred in Tornado Alley and had first-hand accounts of the sky turning green prior to or during the tornado.
Photographic Examples of Green Skies
Here are some photos showing the eerie green sky phenomenon with tornadoes:
A tornado churns under a green tinted sky in Simla, Colorado in 2015. (Credit: Justin Weaver via Flickr)
An ominous green wall cloud producing a tornado near Booker, Texas in 2016. (Credit: Basehunters Chasing via Flickr)
A vivid green sky ahead of a tornado in Sparks, Oklahoma in 2015. (Credit: Pecos Hank via Flickr)
Conclusion
A green sky is a well-known indicator of a possible impending tornado due to sunlight scattering off debris particles whipped high into the air. While not a guarantee that a tornado will form, it should prompt urgent moves to seek safe shelter when spotted. Understanding the science behind the phenomenon provides crucial situational awareness to protect yourself when seconds count. So next time you see skies start shifting to an odd green shade, quickly head to safety before it’s too late!