When a Call Lightning spell is cast, it must be cast outside, otherwise it will not work. The caster is able to call down bolts of lightning. The caster can call down one bolt per turn. The caster need not call a bolt of lightning immediately - other actions, even spellcasting, can be performed; however, the caster must remain stationary and concentrate for a full round each time a bolt is called. The spell has a duration of one turn per caster level. Each bolt causes 2d8 points of electrical damage, plus an additional 1d8 points for each of the caster's experience levels. Thus, a 4th-level caster calls down a 6d8 bolt (2d8 + 4d8).

The bolt of lightning flashes down in a vertical stroke at whatever distance the spellcaster decides, up to 360 yards away. Any creature within a 10-foot radius of the path or the point where the lightning strikes suffers full damage unless a successful saving throw vs. spell is rolled, in which case only one-half damage is taken.