Lightning and Fires
Every year, lightning causes forest, grass, and house fires across the U.S. According to the National Fire Protection Association, lightning causes an average of about 24,600 fires each year and costs about $407 million in damages.
While most fires occur in outdoor areas, lightning starts about 4,400 house fires each year, costing somewhere around $283 million in damages. In addition, wildfires caused by lightning burn an average of 5.5 million acres annually. About 16 fire deaths are attributed to lightning-caused fires each year, most of which are the occupants of houses that ignited by lightning.
Although every lightning strike has the potential to start a fire, some flashes are more likely than others to cause ignition. Most lightning flashes consist of one or more leaders/return strokes. Some flashes contain a continuous flow of electricity, called continuing current. Rather than the charge flowing intermittently in one or more quick surges (return strokes), in continuing current, the charge flows continuously over a longer period of time. This longer period of charge flow causes the struck object to heat up and possibly ignite.
While lightning flashes containing return strokes tend to flicker, flashes containing continuing current appear as a continuously illuminated channel with varying degrees of brightness. Because of the heat they generate, flashes with continuing current are sometimes referred to as hot lightning while flashes containing only return strokes are referred to as cold lightning. Flashes can also contain both return strokes and continuing current.