Fire lookout tower workers locate nearly 80% of wildfires in their areas by watching for smoke and closely observing clouds, since most fires are caused by lightning. Morning skies may bring scattered cumulus clouds, but by mid-afternoon the heat can build them into massive thunderheads, and as storms move across the hills, lightning may strike a tree and wind may fan the flames into a forest fire. Lookouts report wildland fires on both private property and public lands; during one intense lightning storm, sixteen fires were ignited in a single afternoon and reported by the Warren Peak Lookout. When smoke is spotted, the lookout uses an Osborne Fire Finder to determine the general location, then radios the Forest Service office in Sundance, Wyoming, where firefighters are immediately dispatched.