The present invention is an electronic thermostat having correction for the self heating due to the semiconductor switching device used to switch a temperature modifying apparatus on. This invention includes a semiconductor power switching device disposed on an upper portion of a vertically oriented circuit board, a first thermistor disposed on the circuit board at a lower portion thereof remote from the semiconductor power switching device, and a second thermistor disposed on the circuit board at a portion intermediate between the semiconductor power switching device and the first thermistor. A corrected ambient temperature is generated from the temperature indicated by the first thermistor and the difference in indicated temperature between the second thermistor and the first thermistor. The state of the semiconductor power switching device is then controlled based upon the relationship between the corrected temperature and a desired temperature.