To cast call lightning, the character must be in a stormy area—a rain shower, clouds and wind, hot and cloudy conditions, or even a tornado (including a whirlwind formed by a djinn or air elemental of 7 HD or more). The character is then able to evoke bolts of lightning as long as the character remains in the stormy area. (The spell ends if the character leaves the stormy area.) The character can call down one bolt every 10 minutes. The character need not call a bolt of lightning immediately—other actions, even spellcasting, can be performed. However, the character must use a standard action (concentrating on the spell) to call each bolt. A bolt causes 1d10 points of electrical damage per caster level (maximum 10d10).

The bolt of lightning flashes down in a vertical stroke at whatever target point the character choose, within range (measured from the character's position at the time). The bolt takes the shortest possible unobstructed path between a nearby cloud and the target. Any creature within a 10-foot radius of the path or the point where the lightning strikes is affected.

This spell can be used only outdoors. It does not function indoors, underground, or underwater.