A core body temperature monitoring apparatus placed superdermally over a user's skin, including a first temperature sensor, a second temperature sensor, a thermal insulation layer positioned intermediate the first and second temperature sensor and a heater for heating the apparatus and a subdermal tissue region underlying the user's skin. The subdermal tissue region is configured with variable thermal tissue parameters. A controller includes a switch configured for alternating between a calibration mode, wherein the heater is activated for calculating an instantaneous thermal tissue parameter, and a measurement mode, wherein the heater is inactive and the core body temperature is determined, based on the calculated instantaneous thermal tissue parameter.
