Originally Posted by Zinn-X
I bring plenty of water, but don't drink much because it's usually chilly in the morning and I don't sweat much.
No, you mean you think you don't sweat much on a chilly morning. You still sweat plenty, it just evaporates a lot faster so you don't notice it as much. Cramping like you're experiencing is a classic sign of dehydration. I think the fancy electrolyte drinks (gatorade, powerade, accelerade, whatever) help a lot; when you sweat, you're losing more then just water.