I actually kinda enjoy riding in hot weather (and lucky me, I get a lot of it). But there's no question you can overdo it. If you're paying attention to your body, you'll notice if/when you start feeling a little lightheaded, which is a sign to take a break. Wearing a bandana on your head and/or neck and occasionally soaking it will help cool you down. Polar insulated bottles will keep water cool (or at least not hot).

In theory, you can drink so much water that you throw your electrolytes out of balance. I'm not sure how much that would be, but it would need to be a lot. An occasional gatorade cut 50/50 with water will take care of that.