It has been shown and stated many times that waterbenders can control the temperature of the water they are manipulating. It seems to me, however, that this would fall under the ability of a firebender. Waterbending, by definition, manipulates water (in all its forms), and firebending, by definition, manipulates fire, heat, flame, ect. So why are waterbenders able to manipulate the temperature of water?
Exception: It would be logical that waterbenders should, however, be able to effect a phase change (ice to water to steam/vapor ect.) as water appears in all these forms in nature. Other than that however, waterbenders shouldn't be able to manipulate the temperature (of the same phase), as that falls under firebending.
What are your thoughts on this?