Portable electronic device

In a portable electronic device components (2) consuming electrical power during operation may generate heat. A temperature sensor (1) for sensing an ambient temperature (T S ) of the portable electronic device may as a consequence not supply the correct temperature value. It is suggested to provide a compensator (4) for determining a compensated ambient temperature (T A ) dependent on at least the sensed ambient temperature (T S ) and information (P i ) related to the electrical power consumed by at least one of the components (2). After a power down and a reactivation of the portable electronic device, actual internal states (x(b)) of the compensation model are estimated dependent on last internal states (x(a)) stored at the power down, dependent on an estimated course of the sensed temperature (T* s ) between the interruption and the reactivation, and dependent on an estimated course of the information (P* i ) related to the electrical power consumed by the at least one heat source (2) between the interruption and the reactivation.