Ball lightning is the name given to free floating balls of light observed during thunderstorms.
However, ball lightning has been observed to attach itself to objects, especially if these are metallic, or even better magnetic. Therefore, it should be regarded that there are no hard and fast rules yet apparent that can classify any form of ball lightning. It has been suggested that there may be many differing types of ball lightning which would account for this variability. For a full list of characteristics, please see the table below. Sometimes the diameter varies throughout the sighting.