As I've grown older (I'm in my early 40s), I've come to really treasure having the windows open and not having the heat or cooling turned on. Autumn, then spring, are definitely my favorite times of year; all the joys of nature without the extremes.
But I couldn't live without AC. When it's 93 degrees outside and the humidity is over 80%, even with the windows open, a house can become an oven. Apartment living makes it worse, as many apartments don't have windows in walls that allow for cross breezes. And unless I'm playing a game or exercising, I don't particularly enjoy sweating profusely. :-) August in the American Midwest - not to mention the South - pretty much demands AC if you're going to be functional.
More information about text formats