It may also leave a bad smell behind. It usually lasts for only 20 seconds or so, but it can linger for many minutes. Ball lightning generally occurs during high-energy thunderstorms, but not always. Sometimes it appears seconds after a regular lightning strike, or just before. What's more, ball lightning travels in weird ways.
Eyewitnesses describe it moving parallel to the ground.
It can hiss, too. While it's very startling, ball lightning does little damage. Sometimes it leaves scorch marks. Scientists don't exactly know what ball lighting is or why it acts the way it does. These bright, hovering spheres of light seen during thunderstorms have been reported as far back as the Middle Ages.