But even many people accustomed to the look of a menacing green sky don't know what causes ... green skies always herald an incoming tornado. In reality, while it's definitely possible for these ...

A series of severe storms triggered tornado ... sets in the sky. When this light is transmitted by thick clouds composed of water droplets and ice particles, "the results are a green sky." ...

A tornado watch means tornadoes are possible in the area, while a tornado warning means a twister has been sighted or indicated by the weather radar. A tornado emergency is the most severe alert ...