Thunderstorm

A bolt of electricity strikes down from above and flashes across the battlefield. When this spell is cast and at the start of the caster's following turn, each creature in a 20-foot radius, 40-foot cylinder centered on a point within range must make Dexterity saving throw, taking 4d10 lightning damage on a failed save, or half as much on a successful one. If a creature fails this saving throw by 5 or more, they become stunned until the end of their next turn.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the lightning damage increases by 1d10 for each slot level above 4th.