At 120 degrees Fahrenheit / 48 degrees Celsius, the recommended temperature setting for home water heaters, skin requires five minutes of exposure for a full thickness burn to occur. When the temperature of a hot liquid is increased to 140 F / 60 C. it takes only five seconds or less for a serious burn to occur 1. Coffee, tea, hot chocolate and other hot beverages are usually served at 160 to 180 F. / 71-82 C. degrees, resulting in almost instantaneous burns that require surgery to heal.