St. Elmo’s fire is another atmospheric phenomenon that is a feature of thunderstorms. It is a luminous electrical discharge, that occurs from objects when the electrical field around them nears 1000 volts per centimeter. The name was given to the phenomena by Mediterranean sailors, who regarded it as a visit from their patron saint. It was considered to be a good omen, since it tended to occur at the end of the storm when winds and waves were calming. Today, in addition to a maritime event, it is sometimes see surround airplanes as they fly through an electrical storm.
Mary Knapp, Weather Data Library