Summer Rules?

Certainly, you've heard the term "winter rules"  or "preferred lies".  What they mean according to Appendix I of the Rules of Golf, is that under certain adverse conditions (such as those resulting from "heavy snows, spring thaws, and prolonged rains"), a Local Rule can be adopted to protect the course and promote fair play.  The Local Rule will specify the relief procedure, such as allowing a player to lift, clean, and place a ball in the fairway within six inches of where it originally lay.

So is there such a thing as "Summer Rules?"  No.  However, the Appendix allows that "extreme heat" could be one of the conditions that might necessitate a Local Rule.  Keep in mind, however, they're talking about the effects of heat on the golf course (e.g., burned-out areas on the fairway), not on the golfer.  So just because you're hot doesn't mean you can roll the ball over to a better lie.