The temperature of hot tap water varies from home to home, and it depends on the temperature at which the hot water heater is set. Typical home hot water heaters heat water to less than 120 degrees Fahrenheit.
Once the temperature of hot tap water reaches 120 degrees Fahrenheit, there is a risk of serious burns to the skin. While 120 degree water takes about 10 minutes to reach dangerous levels, each degree over that decreases the time needed for serious burns to occur. At 140 degrees Fahrenheit, it takes only about three seconds for the skin to receive serious burns.