Context is everything. Where I live it is usually cool and I can go a long way on not much water. I probably overdrink as a precaution.

But last year in Tanzania at 47C/116F in direct sun I found that I could barely drink faster than I could sweat. On one 50-mile ride I drank seven litres of water - that's over 1.5 US gallons - and couldn't pee for several hours after the finish. Scary.