Call Storm

The caster attempts to summon a storm into the skies above him or her. He or she must be able to see the sky or the spell automatically fails. Whenever this spell is cast, the DM rolls 1d20 for the severity of the storm. The caster has no control over this storm and the storm must run its course before the caster can cast this spell again. Any attempts to cast this spell before the previous spell ends will result in the spell automatically failing.