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 10d6 thunder damage and becomes deafened for 1 minute.

While you are concentrating on this spell, you can protect a number of creatures up to your spellcasting ability modifier from its harmful effects. If you lose concentration the spell remains active, but you are no longer protected from its harmful effects.

Round 2-3. Acidic rain falls from the cloud. Each creature and object under the cloud takes 5d6 acid damage.

Round 4-5. You call six bolts of lightning from the cloud to strike six points of your choice under the cloud. Each creature within 5 feet of such a space must make a Dexterity saving throw, taking 10d6 lightning damage on a failed save, or half as much on a successful one. A creature can only be affected by one lightning bolt and if it occupies a targeted space it has disadvantage on it's saving throw.

Round 6-7. Hailstones rain down from the cloud. Each creature under the cloud takes 5d6 bludgeoning damage.

Round 8–9. Gusts and freezing rain assail the area under the cloud. The area becomes difficult terrain and is heavily obscured. Each creature there takes 5d6 cold damage.  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.

Round 10. The cloud forms a spiraling vortex, as the lightning intensifies before a large explosion causes the acidic rain to catch fire. As the cloud explodes each creature under the cloud takes 20d10 fire damage.