If your going to go out in it plan for it! I was out all day Saturday shooting RC boat races. I made sure I put on the sun screen, brought lots of water, a large umbrella and a chair. When I get too hot, sit in the shade for a bit, drink some cool water, chimp chimp chimp and then go back at it! It does take some adjustment, now I get really cold when it gets below 70!
I always laugh when people say that. I used to live in Phoenix AZ. I took sports pics outdoors....during summer....in 120 degree heat....
They always say there that "oh it's a dry heat", but honestly....120 degrees is still too flippin' hot to take pics whether it's dry or wet. 
