I have a 1/2 perforated leather jacket (sleeves). It has a removable liner so it also works in the winter.
Perforated with lots of vents works well for me up to 95*. I've ridden in hotter, but I don't enjoy that kind of heat.
I have a pair of lighter leather gloves as well. They still have padding on the palms and knuckles, but have mesh on parts of the fingers and top of the hand.
A well vented helmet also goes a long way at keeping you cool. You dump a lot of heat from your head, so it really helps. Just don't get something that looks like it works, most of the glued-on vents don't do much more than make noise. Do some research and find a well vented helmet that works. It does wonders.
And Defy's advice about staying hydrated is extremely important! You have no idea how much you sweat. If you don't stay hydrated you lose your ability to make quick, smart decisions. And that could be fatal on a bike. Always take plenty of drink stops in hot weather.