As long as you have a lightning spell of 2nd-level or higher ready to cast, you may spend a standard action to produce a 40' lightning bolt inflicting 1d6 lightning damage per level of the highest-level lightning spell you have prepared. A Reflex save halves the damage (based on the level of the prepared spell).
As a secondary benefit, you gain +1 to caster level for all lightning spells.
Special
This feat counters and dispels the Storm Bolt feat, which is not fair when compared to Fiery Burst.