An occupant detection system includes an electrode in communication with a detector circuit that detects the impedance of the electrode and compensates for environmental conditions, such as humidity or moisture, based on the impedance measurement. Such environmental conditions may interfere with the occupant detection system's ability to detect the presence and/or size of an occupant. Typically, environmental conditions change the impedance of the electrode. The impedance is determined by measuring a frequency response of the electrode. The measured frequency response is compared to predetermined frequency response values that correspond to known environmental conditions. The environmental condition may be detected by matching the peak frequency response or average frequency response to in a lookup table.