9th-level conjuration

Casting Time: 1 action
Range: Sight
Components: V, S
Duration: Concentration, up to 1 minute

A churning storm cloud forms, centered on a point you can see and spreading to a radius of 360 feet. Lightning flashes in the area, thunder booms, and strong winds roar. Each creature under the cloud (no more than 5,000 feet beneath the cloud) when it appears must make a Constitution saving throw. On a failed save, a creature takes 2d6 thunder damage and becomes deafened for 5 minutes.

Each round you maintain concentration on this spell, the storm produces additional effects on your turn.

Storm of Vengeance After Round 1

RoundEffect
2Acidic rain falls from the cloud.
Each creature and object under
the cloud takes 1d6 acid damage.
3You call six bolts of lightning from
the cloud to strike six creatures or objects of your choice beneath the
cloud. A given creature or object
can’t be struck by more than one
bolt. A struck creature must make a Dexterity saving throw. The
creature takes 10d6 lightning
damage on a failed save, or half as much damage on a successful one.
4Hailstones rain down from the
cloud. Each creature under the
cloud takes 2d6 bludgeoning
damage.
5-10Gusts and freezing rain assail the
area under the cloud. The area
becomes difficult terrain and is
heavily obscured. Each creature
there takes 1d6 cold damage.
Ranged weapon attacks in the area are impossible. The wind and rain count as a severe distraction for the purposes of maintaining
concentration on spells. Finally,
gusts of strong wind (ranging from 20 to 50 miles per hour)
automatically disperse fog, mists,
and similar phenomena in the area whether mundane or magical.