Why the sky turned green | Weather Blog

As a derecho swept across the northern plains on Tuesday, skies turned green. A derecho is a powerful windstorm, but this group of storms brought more than the intense and destructive wind. The ominous green color in the sky is caused by water and ice inside storm clouds and indicates that the storm is producing large hail.

The National Weather Service office in North Platte, Nebraska created this great infographic explaining what is happening inside the cloud. In a very general sense, this is the same reason we get rainbows. The light we receive from the sun actually exists in the colors of the rainbow (red, orange, yellow, blue green, purple), and water in the atmosphere can scatter this visible light into these different colors under the right circumstances.

“Water/ice particles in thunderclouds with substantial depth and water content will primarily scatter blue light. When reddish light scattered from the atmosphere illuminates water droplets/ blue ice in the cloud, they will appear to glow green. It takes a lot of water (…) to get that color, which usually means that a substantial amount of ice (large hail) must be present!”

There were dozens of images like these online when it happened. Some have been changed, so choose carefully which ones to believe. To the best of my knowledge, the photos included here do not appear to have been altered. This is the color the sky seemed to have on Tuesday afternoon.

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