Ok... So the gym has never reached this level before, so I guess I had better explain them all...

Mist - Mist was designed here to work as the games

Haze - Haze was designed to function as it does in the games, but happen every action after it is activated (so status changes only last one action)

Super heavy rain - As mentioned in the description, Super Heavy rain doubles the power of normal rain, and causes damage over time to Rock, Fire, and Ground types, as if under the power level of Sand Storm / Hail

And my moves for this turn:

Synthesis ~ Giga drain ~ Synthesis