Why do some thunderstorms produce greenish-looking skies before they strike?
Quick Answer
A green tint can appear when very dense storm clouds scatter light in a way that makes sunlight look greenish, often because of heavy rain and hail inside the storm. It does not always mean a tornado is coming, but it can signal severe weather.
The Full Story
The exact cause of green skies is still debated, but the effect is usually linked to intense thunderstorms with thick clouds, hail, and lots of water droplets. The storm structure can filter sunlight so that shorter and longer wavelengths are scattered differently, sometimes giving the clouds a green cast. The color is most often noticed late in the day when sunlight is lower. While not a perfect tornado warning, green skies often occur in storms that are severe enough to produce hail, damaging winds, or tornadoes.
Key Facts
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