I drink more than that.
But in those conditions you could very well go through more than that. Remember no air conditioning and alot of folks are out in the sun and there is basically no transportation exertion makes you drink much more. Dehydration is a real concern!
Amazing -- I couldn't drink that much if I tried without getting ill. Mow my own grass in the all kinds of heat here in OK but no way could I drink a gallon of water.