Probably normal, but do you have anything else going on? When I recently had the extreme thirst/dry mouth thing going on I also had some blisters forming on the inside of my lower lip...weird. So I looked it up in one of my homeopathic reference books and, sure enough, there was a remedy for those things together, sulphur, IIRC. I took one dose and everything cleared up. Of course I still make sure that I drink loads of water everyday.
Oh, and if you want to try a drink, see if you can find Recharge instead of Gatorade. I know that they carry it at Wild Oats, but not sure if it's available everywhere. It's what my midwives recommend having on hand during labor and is IIRC, just a little more natural than the gatorade mixture.