The normal resting human body temperature is commonly cited as 37 °C.
This figure is an average rather than a universal constant. Measurements vary with the person, time of day, activity, age, hormonal state, and the site and method of measurement. Body temperature is generally lower in the morning and higher later in the day because of circadian rhythms.
The hypothalamus helps regulate core temperature by coordinating heat production and heat loss. Sweating and increased skin blood flow promote cooling, while shivering and reduced skin blood flow conserve or generate heat. Fever occurs when immune signals raise the body's regulated temperature set point.
Historical measurements helped establish 37 °C as the familiar reference value, but modern population studies show that average temperatures can be somewhat lower. Oral, ear, rectal, and armpit readings are not directly interchangeable, so a numerical result needs measurement context.