A leader of a bolt of lightning can travel at speeds pf 60,000 meters per second (13,670 miles per hour), and can reach a temperature approaching 30,000 degrees Celsius (54,000 degrees Fahrenheit), hot enough to convert silica into glass. Large bolts of negative lightning from the clouds carry an electric current of up to 100,000 amps. Lightning rapidly heats the air in its immediate vicinity to about 20,000 degrees Celsius (36,000 degrees Fahrenheit), about three times the temperature of the surface of the sun. This compresses the surrounding air and creates an acoustic wave that is heard as thunder.

In the following image, you can see many "failed leaders" that were false starts for the negative charges on their way down. Note that there were several negative leaders close to the ground; one of them matched up with a positive leader and became the major lightning bolt (return stroke), leaving several smaller failed ones. You see the failed negative leaders since electrons still take all paths downward in the previously ionized channel. You don't see the failed positive leaders since they aren't connected to any electrons from the clouds.