The heat, definitely. I have room air conditioners but my living room gets hot and it's hard to keep up with the exercise. And I enjoy walking at a park near my office, but not when it's in the 80s.

SmallSteps, years ago, I heard sportscaster Bob Costas complain about the heat in Arizona, to which someone countered "But it's a dry heat." He responded: "So is my oven, but you don't see me sticking my head in there!"