If you're looking for a little adventure out of the Summer heat, Tempe Center for the Arts is the way to go... Docents are available walk you around and explain some of the intricacies of the building you might not otherwise have noticed or even thought of. Some of the features, such as the theater dome, are particularly impressive.
A small art gallery is also open in the center - fun and interesting pieces - some are even interactive like an amped knarl of roots that functions as a drum set... The gallery, along with the rest of the complex, is open Tuesday-Saturday 10AM-6PM during the summer.
Check it out!