The worst hangover I had lasted for 2 days, I was repulsed by the sight/smell of food, felt nauseous and had a constant headache. I don't drink often, but when I do, I make sure to take Tylenol and drink plenty of water before bed, and find that it really helps.
At this point, there isn't much you can do. Like previous posters, I recommend drinkings lots of water (especially since you are already dehydrated and it is really hot outside), eating a little, and getting rest. Hope you feel better!
I drank a whole 2 6 of Jack Daniels straight by myself one night and ever since; I can't even stand the smell of hard liquor.