Why does the sky sometimes turn green when a tornado approaches?
Accounts of thunderstorms that appear green are rare, although records of their observation go back more than a century. They are often regarded as harbingers of severe weather, including tornadoes. Several hypotheses over the past 25 years have tried to explain the phenomenon, ranging from the relative positions of the sun, storm clouds, and the observer to the reflection of sunlight off of hail inside the clouds or off of green foliage on the ground. One of the two leading hypotheses suggests that storm clouds act as a sort of dark backdrop, against which sunlight scattered by air molecules will appear blue. Combining this with the reddish color of the sun at sunset can give the clouds a greenish appearance. The other hypothesis suggests that the green color comes from the thunderstorm itself, with the absorption of light by liquid water or hail within the thunderstorm clouds providing blue light, which combined with the red light of sunset, creates the greenish appearance. A 1995 st
