Tempest Strike

You channel storm energy into your weapon. Make one melee weapon attack with a weapon you’re holding. Use Charisma for the attack and damage rolls. On a hit, the weapon deals its normal damage, and the target takes an extra 1d8 lightning damage.

At Higher Levels: The lightning damage increases by 1d8 at 5th level (2d8), 11th (3d8), and 17th (4d8).

Storm-Synergy: If you cast this in your Conjure Storm area or within 10 feet of water, increase the lightning damage by one die size (for example, 1d8 → 1d10).*