Ball lightning
Ball lightning would always produce itself during my local thundersnow episodes. They'd drop down from about 30 feet in the air and bounce about like a particularly happy bubble, burning the feck out of everything they touched.

One came through my friend's phone, bounced around the house, decided it needed some fresh air so burned its way through the wall.
(TheSnark oh, c'mon, like you didn't see me coming, Fri 4 Jul 2008, 19:26, Reply)