Q: Since lightning is electricity, how hot can a lightning bolt be?
A: Hotter than you probably think, says Brent McRoberts of Texas A&M University. “Scientists have done numerous experiments on this very subject,” McRoberts explains, “and the air around a lightning bolt can reach as high as 54,000 degrees. That’s over five times hotter than the surface of the sun. 
That’s why when the air gets that hot, it expands faster than the speed of sound, and the compressed air around it sends out a quick shock wave — and that’s thunder. And since one bolt is really several bolts strung together, there are several of these shock waves one right after another, each at a different altitude. That’s why thunder often seems to rumble.” Whereas for the hot days.