Helly, welcome to the forum !!! I can't help you on how to deal with 100F heat, it was nearly 90 here in NY yesterday and I could not think about going out to ride I think one needs to sort of get used to the heat to be able to ride. I would suggest lots and lots of sunscreen, also try to get your electrolites from drinks or pills that don't contain a lot of sugar. Personally, on a hot day in the summer, I always crave cold watermelon YUM. Dress light, and wear light colored helmet.