It has been said that room temp is better because it doe not shock your system.
Most people find it thirst quenching in hot summer heat to drink something icy cold. It is ok so long as you are not eat food at the same time. The cold water will put your stomach juices in shock and it will slow down digestion. If you eat something greasy (fries and a burger)and the water is icy cold, the oil will harden like lard. EEWE! It is better to drink a hot tea if you are eating anything greasy.
So...room temp is better. Icy cold when it is the only thing you are consuming. Then give yourself 20 minutes before eating. Let the water absorb through your system.