I like to go mountain biking but I live in Phoenix, AZ. It gets so hot here that it really isn't safe to exercise outdoors for several months out of the year. Maybe early in the morning but I'm never up that early.
I went mountain biking year round in Phoenix when I lived there, and I'm terrible at getting up early. Fill up that Camelbak and you'll be fine. I also cycled 15 miles to work on my road bike, on what turned out to be the hottest of the prior several years (116, I rode in around 11am).
