“St. Elmo’s fire (also St. Elmo’s light is a weather phenomenon in which luminous plasma is created by a corona discharge from a sharp or pointed object in a strong electric field in the atmosphere (such as those generated by thunderstorms or created by a volcanic eruption).”
“Physically, St. Elmo’s fire is a bright blue or violet glow, appearing like fire in some circumstances, from tall, sharply pointed structures such as lightning rods, masts, spires and chimneys, and on aircraft wings or nose cones. St. Elmo’s fire can also appear on leaves and grass, and even at the tips of cattle horns. Often accompanying the glow is a distinct hissing or buzzing sound.” -From the wiki page.