According to the Miami Herald, David Canales, a landscaper, was killed this past Thursday by lightning that came out of a clear blue sky. It's a bizarre phenomenon called a "bolt from the blue":
Dan Dixon, a meteorologist with the National Weather Service in Miami, said that when Canales was hit, a typical afternoon storm was forming but nowhere near the area.
Weather data showed that lightning activity picked up north of Pinecrest shortly before 1 p.m., as a storm gathered momentum and swept through Coral Gables and then downtown.
The bolts normally travel horizontally away from the storm and reach farther than typical lightning, then curve to the ground. . . .
Dixon said protecting yourself from such unexpected lightning is difficult.
''They are very unpredictable and very dangerous. We urge people to stay indoors even if you hear thunder only faintly in the distance,'' Dixon said. ``If you're close enough to hear thunder, you're close enough to be struck by lightning.''
The photo is from NOAA
That's not true. Lightning can strike cloud to ground, cloud to cloud, or ground to cloud. Therefore, depending on how you measure the current, you can get a positive or negative number.
However, that current is always electrons flowing, the -/+ sign is just a way of saying which way those electrons are going. Therefore, lightning bolts themselves are always negatively charged. A positively charged lightning bolt would mean protons are flowing (which they don't do).