the problem with cooler temps is you don't Think you need as much water but you're still losing it by sweating and breathing with your mouth open. Because the temps are cooler and you're wearing fabrics that wick you may not realize just how Much you're sweating. The nicest thing I ever read was: your body will get rid of the excess water if you take in too much! So drink drink drink. I try to drink at least a bottle an hour every season of the year except summer: when I try to drink more.