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How does moisture contribute to lightning and natural wildfires?

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Earth A composite image of Earth captured by instruments aboard NASA's Suomi National Polar-orbiting Partnership satellite, 2012.

Moisture is a fundamental component in the development of both lightning and wildfires, though it influences them in distinct ways.

Moisture and Lightning

Moisture is essential for the formation of thunderstorms, which generate lightning. When moist air rises, it undergoes condensation, releasing latent heat that fuels further upward air motion and atmospheric instability.1

Within these deep, vigorous clouds, moisture facilitates the growth of precipitation, including hail. Many experts believe lightning is closely associated with the presence of precipitation, particularly soft hail; the electrical charge and strong fields are thought to be produced when ice crystals or cloud droplets collide with and bounce off the undersurfaces of these hail pellets.2

Moisture and Wildfires

While moisture drives the storms that create lightning, the absence of moisture—or drought—is a primary factor in wildfires. Wildfires most frequently occur during a region's driest season, as low moisture levels increase the flammability of vegetation. Lightning strikes from the storms described above are a leading natural cause of these fires, which then spread more intensely under conditions of heat, wind, and continued drought.3