Originally Posted by DrIsotope

Personal best: 64 miles in 3h30m (moving,) average ride temperature 102º, high temp 113º; during ride, drank seven 25oz water bottles, plus roughly 32oz water at stops that never made it into the bottles, for a total of 207fl/oz. This means I drank just about 13.5lbs of water. I drank an entire 25oz bottle in the final 10 minutes. Stepping on the scale post-ride, I had lost a bit over 7 pounds, meaning I put out almost 21lbs of sweat. Nearly 6lbs per hour.

I think I'm perpetually dehydrated, despite taking in well over a gallon on a typical summer day, not including water during my daily ride. Hot days can routinely exceed 2 gallons. As such, my weight can fluctuate 8-10lbs over the course of a day-- though I am a fair bit bigger than everyone else in here, around 215lbs.