What conditions create the dry thunderstorms that plague western firefighters? Specifically, why do some of them not produce any rain?
-- Kate Abrell
A “dry” thunderstorm is one that produces lightning but little rain, as illustrated in the photo on the facing page. Dry thunderstorms create problems for firefighters because the intense heat of the cloud-to-ground lightning starts fires that spread easily, since there is little to no rainfall to put them out.
During the weekend of June 21-22, 2008, dry thunderstorms in Northern California produced 5,000-6,000 cloud-to-ground strikes (a lightning detection network counts them), which ignited many hundreds of wildfires in the area. Most were small and quickly extinguished, but some burned thousands of acres and cast a pall of acrid smoke over populated areas.