Slip, several times when we were in PA they closed schools because of the heat - of course they weren't air conditioned. ;^)
The first driving tip Cyber gave me when I moved here was this: A person in the heat of the summer with his windows rolled down ALWAYS has the right of way. Reason? They are so hot, that road rage can be a problem. Best to let them get some wind on their faces, albeit hot wind. It's not on the books as a law, but just common sense.