Hot water that is comfortable for washing hands is not hot enough to kill bacteria. Bacteria grows much faster at body temperature (37 C). However, warm, soapy water is more effective than cold, soapy water at removing the natural oils on your hands which hold soils and bacteria.
Laestadius JG, Dimberg L (April 2005). "Hot water for handwashing—where is the proof?". J. Occup. Environ. Med. 47 (4): 434–5.
Contrary to popular belief however, scientific studies have shown that using warm water has no effect on reducing the microbial load on hands.
You've probably been told that it's best to wash your hands in hot water because it helps to kill bacteria, but that is actually not the case. Adult skin can begin to scald at 120 degrees Fahrenheit (49 degrees Celsius), but studies have shown that hands washed using water up to that temperature still don't remove bacteria