I have a set of perforated leathers for summer riding. Underneath, I wear shorts and a tshirt/ss shirt. (just happens to be what I wear to work as well) It's very comfy up to about 90. After that, I do the camelbak/wet shirt thing on long rides. Long red lights are a bitch, so I generally try to find routes without them.
It's also great because I can strip the leathers off at my destination and be in comfy. It only takes a minute or two to do the transformation and I don't even need a phone booth. Which are getting hard to find these days.