Abstract: A hygrometer includes a capacitive sensor with a capacitance that changes in response to water or ice forming on its surface. A controller controls a thermoelectric module to cool the sensor until dew forms on the surface of the sensor. The controller then controls the thermoelectric module to heat or cool in response to a sharp change in the capacitance of the sensor, which occurs at the dew (or frost) point temperature of the ambient air, until the sensor reaches equilibrium at the dew (or frost) point temperature.