Growing up in Oklahoma, I have seen a green sky more than a few times and there is normally a strong storm following. I never really knew why, but I always knew that when the sky turned green, it was time to go inside and turn on the weather channel.

For hundreds of years, there have been reports of green skies, primarily before severe weather, but still today, scientists can’t seem to agree on exactly why it happens.

Brent McRoberts of Texas A&M University says, “The most popular theory is that thunderstorms contain a lot of water – often in the form of hail – and this water or ice tends to scatter green light during the strong updrafts that occur in severe storms…”
This helps us understand the science behind what is causing the green sky, but it is still uncertain why, under the right circumstances, it isn’t always green.

Scott Bachmeier, a research meteorologist, states that “green is significant, but not proof that a tornado is on the way.” He continues saying, ‘Green does indicate that the cloud is extremely tall, and since thunderclouds are the tallest clouds, green is a warning sign that large hail or a tornado may be present.”

We may never know the real reason behind green skies because research for green thunderstorms is limited due to lack of funding, but Bachmeier offers some alternative folk wisdom for the color change: that tornadoes sucked frogs and grasshoppers into the sky.