Climate and Weather History

How can I find out how many lightning storms affect various parts of the country?

After a rather long search of the Internet, I found nothing on-line. (If anyone reading this knows of a site with a map of lightning frequency, please let me know!) There is a printed publication, Thunderstorms and Lightning... The Underrated Killers, which is a preparedness guide from NOAA, FEMA, and the American Red Cross. Inside is a map of "thunderstorm days" across the contiguous United States. This is somewhat different than the number of lightning storms, in that there could be several storms in one day at the same location. The publication is available from the National Weather Service Office nearest you.