Next time, try starting your "long" rides early in the morning (if it's on a weekend). On weekdays (after work), I only do "short" rides of 25-35 miles, carrying 2 bottles with me.
Freeze the water bottles,and you'll have cold water on the way home.
Good points, all. I usually do ride in the mornings, but my schedule conspired against me last weekend. I'll definitely pack more ice next time, and stop for breaks periodically.