I ride all summer long and at least one of my friends thinks that I'm crazy. I used to work outside every day so guess I sort of got used to it. We certanily got lucky this year with several cooler months.
Can't imagine taking the summer off from riding. Are there people who do that? I'm not talking about just cutting back to once a week but rather hanging the bike up until cooler weather arrives.
I also ride dirtbikes and it is very rare that we go out in the dead of summer so I guess it wouldn't be that odd if some do the same in mtb'ing. Wearing all the dirtbike gear is like being in a sauna though. Long pants, long sleeves, knee high boots,knee guards,camelbak,full face helmet and goggles, and sometimes a chest protector. It really takes the fun right out of it for me.