Proper temperature gradient

I'm gonna revive this thread with a new question:

Michigan is finally starting to get warm! In fact, there are theoretically going to be some days soon where the high reaches into the high 80s and low 90s. Is there anything I can do to cool my tank a bit when the ambient temperatures of the house (no air conditioning) are so high?

Oh - I figured I'd add this:

The only solution that I could come up with was moving the tank into the basement, where it's quite a bit cooler. I'm hoping somebody's got a better suggestion than that, because (a) I just moved this guy into his tank yesterday, and I don't want to stress him out again, and (b) I really don't spend much time in the basement, so I wouldn't be able to keep as close an eye on him and his habitat as I do now.