My gut response after reading this question was: Well, duh--obviously, summer is more conducive to happiness. I mean, you can make a good case for the virtues of spring and fall, but they're really less seasons than they are opening acts. And apart from Christmas and skiing, winter doesn't have a whole lot to recommend it. Nope. If you're ranking seasons, summertime is the clear winner. Summer=hot sun, slow, quiet afternoons, and water-logged family vacations. What more does a human being need to be happy, apart from an air-conditioner and an ample supply of snacks?