I don't know what makes it so but the more the mercury rises the better a hoppy beer refreshes. I confess I drink them in any temperature and am a certified hopaphile drinking them as hoppy as I can get them. There is something extra refreshing about the citrus flavors in an IPA or ESB that quenches that summer heat. Central City's Red Racer IPA, Russell's Blood Alley Bitter and Cannery Brewing's IPA are some of my BC favorites.
I have some of these in the fridge almost all the time. (Unless we have lots of company and then they disappear pretty fast)