A year ago, exceptional drought — the most serious kind — covered 40 percent of California. As of Thursday, following weeks of heavy rain storms and massive dumps of mountain snow, exceptional drought has vacated the state. The intensity and coverage of California’s drought has shrunk dramatically since October when 80 percent of the state was declared a drought area by the U.S. government’s Drought Monitor. Now just about half the state has drought conditions — entirely focused in central and southern California. The Drought Monitor indicated that Northern California was drought-free two weeks ago.