If you were to look outside your home during a thunderstorm and see a tall streetlamp glowing with blue flames, you might be tempted to call the fire department. Then you might notice that the streetlamp is on fire but isn't actually burning -- and the water from the fire hose isn't putting out the flames. At this point, you might be about ready to call a priest, but that, like the call to the fire department, would be unnecessary. The phenomenon you're witnessing is actually St. Elmo's Fire. (Which has nothing to do with a 1980s coming-of-age film starring a young Emilio Estevez.)
St. Elmo's Fire is a weather phenomenon involving a gap in electrical charge. It's like lightning, but not quite. And while it has been mistaken for ball lightning, it's not that, either -- and it's definitely not fire.