A secondary is really just a storage vessel for the beer while you wait for it to clear or whatever. So, any temp that is fine for storing beer will be fine for keeping your secondary, though cooler (like cellar temps ~ 55F) is probably better. I like to keep my secondary-ing beer in my fermentation fridge if I have room. Otherwise, it goes in my coat closet, which is at room temp.
Long story short, as long as you don't freeze it or let it get too hot, the beer will be just fine.