Quote from Bert in the episode Spoiler: Bert is Magic
Keith: There are legends of sorcerers capable of controlling the weather, but no one's ever witnessed it. Bert: Wait. So you guys think that I'm the one who made it...? [mob agreeing] 'Cause I did. [mob laughs] Rain, snow, hail... I do all your precipitation. Female Mob Attendee: Are you in league with a demon? Bert: Oh, no, I just ask nicely. You know, "Please rain." [it rains] [mob gasps] Ta-da!