Skin temperature is a measurement of the heat in the outermost surface of the body. It can be significantly lower than your core temperature in the limbs and extremities.
Normal skin temperature for healthy adults ranges between 92.3 and 98.4 Fahrenheit or 33-37 Celsius, far lower than the 98.6 F average core temp. Changes in skin temperature may indicate potential illness or injuries.
Your skin is your largest organ, making up approximately 15% of your total weight. The surface volume of skin means there are regional variations in temperature. The skin of your fingers and toes may be drastically lower from the temperature taken on your forehead. Having such large surface volume means that your skin plays a significant role in regulating your body temperature. This is called thermoregulation and allows your body to preserve or discharge heat based on its needs.
For example, as you near your normal bedtime, your circadian rhythm cycle prepares your body by drawing heat away from the core, slowing your activity level and lowering your metabolism. This action allows your core temperature to slowly decrease, starting the sleep cycle, and prepares the body for other natural processes such as producing hormones, cell regeneration and immune system responses.
Additionally, in cold conditions your body can draw heat away from the skin to keep your core temperature stable.
High skin temperature may indicate fever or illness, but it may simply mean you are too close to a heat source, or you had too many blankets over you while you slept. Working out may also temporarily affect skin temperature.
Significantly low skin temperature may mean you are suffering from hypothermia, and the body is drawing off surface heat to keep your core temperature high. But, low skin temperatures may also be less serious. You could be sitting in a chilly room or too close to an air conditioner.
WHOOP 4.0 includes a skin temperature sensor that allows you to track your daily skin temperature in the new Health Monitor feature. WHOOP uses data from your previous 90 nights to personalize a baseline for your skin temperature. You can use the data in conjunction with the updated Sleep Coach to experiment with factors while you sleep to see if those changes help you sleep comfortably. For example, if your skin temperature registers as high even on cold nights, you might consider taking off a blanket or turning on a fan.
The products and services of WHOOP are not medical devices, are not intended to diagnose COVID-19, the flu or any other disease, and should not be used as a substitute for professional medical advice, diagnosis or treatment. All content available through the products and services of WHOOP is for general informational purposes only.