There is a fine line on drinking too much water, most of us never have to worry about reaching that line.
Riding in humidity is a fact of life here on the east coast, I find that if I don't drink enough before the ride, during the ride and after the ride, I pay for it the next few days as my body craves liquid but it just flushes out as I have no need for it(at work no need for the extra water). I still get exercise as the closest facility is 6 flights down the stairs.