Not great.
It rarely gets below 40F around here, but in the summer we'll see thirty or forty consecutive days of 100+F weather, so it gets very hot in the attic.
That's another reason why I'd like to reach a point where I've got things organized and tested, and can identified which members I am willing to cull from the herd. The fewer seasons spent in the attic, the better. Of course, they may just end up in someone else's attic...