Wednesday night’s storm, which stretched more than 700 miles from eastern Iowa to northern Virginia, produced more than 1 million lightning events over 18 hours — more than 236,000 of them occurring in Illinois and over Lake Michigan, and is blamed for a house fire in Evanston.

Since 1989, every stroke and flash of lightning that happens in the continental U.S. has been recorded in real time by the Vaisala-owned National Lightning Detection Network, based in Tucson, Ariz., which monitors lightning activity 24 hours a day, 365 days a year. This includes the time, location and polarity of cloud-to-ground lightning and cloud pulses, which can stay in a cloud or be connected to cloud-to-ground lightning. READ MORE