Wildfire Causes

Wildfires can be caused by nature—like lava or lightning—but most are caused by humans.

Humans and Wildfire

As many as 90 percent of wildland fires in the United States are caused by humans. Some human-caused fires result from campfires left unattended, the burning of debris, negligently discarded cigarettes and intentional acts of arson. The remaining 10 percent are started by lightning or lava.

Human caused wildfire

Cigarettes are one way humans can cause fires.

Nature and Wildfire

Lightning is described as having two components—leaders and strokes. The leader is the probing feeler sent from the cloud. The return streaks of light are a series of strokes that produce the actual lightning bolt or flash that we see.

There are two types of lightning—cold lightning and hot lightning. Cold lightning is a return stroke with intense electrical current but of relatively short duration. Hot lightning has currents with less voltage, but these occur for a longer period of time. Fires are usually started by unusually long-lasting hot lightning bolts.

Lightning over the Grand Canyon.

Lightning is one of the two natural causes of fires.