I live in the Southern California desert. This is what I do when it is hot--as in over 100:
1. Water...lots of it, in the saddlebags, down the throat.
2. Cooling vest soaked in water.
3. Armoured mesh jacket over the vest.
4. Armored mesh over pants.
5. Tactical, breathable boots.
6. Stop every 45 mins to hour to drink water and resoak the vest with water.
7. Helmet, open face with lots of vents.
8. Sunglasses
9. Mesh type racing gloves.
10. ABSOLUTELY no beer.
If I stop sweating I stop riding immediately and guzzle water until I start sweating, then wait to cool down before I start riding again.
It is a pain in the a$$ getting ready to go, but when I went down, I got back up. I slid on the pavement about 40 feet. I still have a head because of the helmet. I had ONLY a dislocated shoulder and two cracked ribs because of the jacket. I had no road rash at all. My feet were not injured. I had chipped a piece off my kneecap, that is still "loose" in my knee. (Did you know that injuries to toes, feet, and ankles account for 39% of motorcycle based injuries and that boots eliminate 73% of those injuries.). Edit: I forgot my hands: they were completely uninsured. My $90 riding gloves were destroyed though.
people who don't gear up are, in my opinion, no different than adolescents who deny that taking drugs can seriously hurt them. Gearing up is just part of the sport. If someone wants to be cool, warm, not need to use muscles and get tired, or if one wants things quiet without using ear protection, then a motorcycle is not for them.
...and, yes, there are times when it is too hot for me to Ryde. When it is 105 or more, I use an air conditioned cage...and I ride about 13,000 miles a year.