Vyvo Devices only measures the temperature of the waist area; therefore, we strongly suggest you to perform a Skin Temperature measurement when your waist hasn't been exposed to any source of heat and cold to obtain a neutral result.
For example, a circumstance where you've been driving with your device worn on the arm exposed to the sun, or if you perform a measurement right after your wearing arm has been in contact with ice or snow, may affect the measurement result.