Clouds and the ground can act in unison to mimic a huge natural capacitor. The process of evaporation and condensation of atmospheric water within clouds causes water droplets to collide with dust, ionizing radiation, and each other.

These collisions cause electrons to be knocked off the particles creating a charge separation in the clouds. Negative electrical charges accumulate at the base of clouds. The base of the clouds can be compared to a negative plate of a capacitor. These charges induce positive charges to accumulate in the ground, comparable to the positive plate of a capacitor. The air between the clouds and ground becomes the dielectric of this natural capacitor. The electrostatic field between the clouds and the ground can produce ions and free electrons in the air. Eventually the difference in potential between the clouds and the ground can become so great that the air dielectric begins to break down. The ions and free electrons provide the necessary path that short-circuits this natural capacitor, initiating a flash of lightning.