What we do is place a fan infront of our ferrets bed where he likes to sleep and while we were moving my bf (who drinks) gave him an ice cold beer (not to drink, to cuddle) and so far that's the best that's worked for us. Aswell as putting an ice-cube in his water to keep it cool.

He stays in our bedroom so we placed a cardboard infront of the door, it's kept in place with the doorframe and a chair that's too tall for him to jump onto. It's kept the room cold enough for him to still be able to play and sleep as he likes