I would advise something a lot simpler:
Weathers: Rain, Sun, Sand, Snow, Strong Winds (5)
Terrains: Grassy, Electric, Psychic, Misty (4)
Rooms: Trick Room, Wonder Room, Magic Room (3)
Every turn, it steps through each room/terrain/weather in order. Since there are 5 weathers, 4 terrains and 3...