Tweeti am going to go against you on this one tillt and here is why: i have attended numerous extreme hot and extreme cold weather training packages around the world and what they teach is this: if you consume ice cold water or hot water your body will force it back out through your urine. the reason behind this is that your body doesnt want to use energy to bring it up or down to body temp. they had all these fancy charts and studies and blah blah but the take home message that i got from the experience was that room temp or body temp water is best for rehydrating or hydrating in general. now i am not going to say that hot and cold liquids dont warm and cool you down but in optimum operating environments room temp is the way to go