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Rolling thunder caused by shock waves Aug 12, 2017 12:00 AM A A I can understand why lightning makes a short, loud cracking noise, but why does it sometimes make a long, rumbling noise? — Aaron, Medford A lightning bolt can reach 54,000 degrees — five times hotter than the surface of the sun, according to the National Weather Service. When the air around the bolt is heated to such temperatures in just a fraction of a second, a phenomenon known as "explosive expansion" occurs. The super-heated air expands so rapidly it compresses the air in front of it, triggering shock waves, NWS says. The initial sound of lightning reaches the ear with a loud bang or crack, NWS says. But as the shock waves continue to travel away from the strike, they become stretched and distorted, producing a more muted sound. When the shock waves reach a person who is far from the lightning strike, the listener will hear a continuous booming and rumbling sound, according to NWS. — Send questions to “Since You Asked,” Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to [email protected] . We’re sorry, but the volume of questions received prevents us from answering all of them.