+1. When in the rain I usually ride with fenders. However, that have been a few times when, for various reasons, I wanted to ride one of my bikes in the rain without fenders. On those occasions, I use the backpack/bladder system. I don't find the weight a problem; and given it's raining, being too hot is not a problem. I do dislike the extra work in keeping the bladder clean. With my water bottles, the simply go in the dishwasher after each ride.