According to David Cook, a meteorologist at the Argonne National Laboratory, lightning flashes in the clouds over earth about 40 million times a day; approximately 4 million of those flashes actually strike the earth. Lightning discharges or "travels" at about 1/3 the speed of light or 62,000 miles a second and heats the surrounding air anywhere from 20,000 to 100,000 degrees F, or up to 10 times hotter than the surface of the sun. This incredible heat produces the sound waves that we hear as thunder. In the U.S., central Florida has the highest number of thunderstorms. The lowest number occur along the Pacific coast region from northern California up through Oregon and Washington, as well as in Maine. In the forest belt of the Pacific northwest, however, even infrequent lightning can create havoc. Dry lightning is the greatest natural cause of wildfires, including the Mendocino Lightning Complex of 2008.

Primary Sources

Email from Stephen D. McGregor (Argonne National Laboratory) to Doris Schoenhoff (MRC) on 8 September 2008, including forwarded email from David Cook to Stephen D. McGregor.