A numerical rating from the lowest of 1 to the highest of 6, keyed to the start of thunderstorms and the frequency and character of cloud-to-ground lighting forecasted or observed on a rating area during a rating period
US Forest Service, Glossary of Fire Behavior & Fire Weather Terms, Washington, D.C., USA 2010. http://www.erh.noaa.gov/phi/fire_glossary.htm, (For Fr - Amer) {505}