Described embodiments include a portable electronic device. The device includes a shell housing components of the portable electronic device having a heat-generating component. The device includes a heat-rejection element located at an exterior surface of the shell. The heat-rejection element is configured to reject heat received from the heat-generating component into an environment in thermal contact with the heat-rejection element. The device includes a controllable thermal coupler configured to regulate heat transfer to the heat-rejection element. The device includes a proximity sensor configured to determine a location of a user touch to the shell relative to the location of the heat-rejection element. The device includes a thermal manager configured to regulate heat transfer by the controllable thermal coupler to the heat-rejection element in response to the determined location of the user touch relative to the location of the heat-rejection element.