Generally I like to use lukewarm to slightly warm water (105-110F...or around 40C)

I find too warm or hot is too drying (plus I turn bright red) and cool or cold doesn't seem to help my cleanser remove my makeup.

I don't splash with cold water since I know that pores don't open and close that way (contrary to popular belief), and cold water can be irritating. I wash with warm since it helps boost the detergency of my cleanser..