A nurse says the female patient's temperature is 31 degrees Celsius (C) and the ambient temperature last night was 10 degrees. That is about 88 degrees Fahrenheit (F). Hypothermia, which is generally a temperature lower than 95 degrees F, can begin anytime a body's temperature is lower than the normal 98.6 F. The US Coast Guard says in water under 32 degrees C, expected survival time is only 15-45 minutes. In calm wind conditions in 10 degree F weather, frostbite can begin in under 30 minutes.