What makes a storm green

Many cloud-watchers have noticed the peculiar green tint that sometimes appears in the heart of a strong thunderstorm. A popular explanation had it that hail or ice in the storm was refracting and absorbing the light to favour green wavelengths. In the mid-1990s, a pair of scientists took a spectrophotometer to Oklahoma and Florida, hunting for green storms. They found fifteen cases where various shades of green appeared. Some possible causes were ruled out; for instance, the green wasn't being reflected from vegetation. However, some of the hail-producing storms failed to produce green cloud at all. The results hinted that more than one factor must be at work behind this distinctive hue.