In a portable electronic device, a temperature sensor is provided for sensing an ambient temperature of the portable electronic device. At least one other temperature sensor is provided for sensing a temperature inside the portable electronic device. The portable electronic device further comprises a set of components radiating heat in an active state in response to the consumption of electrical energy. A calibration module is adapted to conduct a calibration measurement during or in connection with an active state of at least a first component out of the set, and is adapted to determine a set of calibration parameters in response to the calibration measurement for adjusting the at least one sensed inside temperature. A compensator is provided for determining a compensated ambient temperature dependent on at least the sensed ambient temperature and the at least one adjusted sensed inside temperature.