There are conventions present in western society that cause us to immediately associate certain forces with various colours: fear and disease are black; fresh, wild things are green. These associations have even made it into our colloquial speech - we have black death and black hearts, and someone who is new at something is described as being "green". Ask almost anyone and they will tell you that heat is red, and that water is blue. There are similar connections made with shapes and patterns that are not perhaps as strong but still exist. Water is waves, ripples, droplets. Heat is not tangible in the same way as water, but we still tend to think of it in rays and waves.
If I was trying to represent water or heat in a textile, I would stay in line with these conventions for the sake of recognizability. For water, I think I would either use a wide sine-wave pattern aligned length-wise, or short diagonal stripes. I would use shades of blues and pales greens. For heat, I would use narrow waves arranged width-wise, alternating between reds, oranges and yellows. For heat I might also use an ombre fading from black through red, orange, yellow and ending on white.