Wireless transmitting sensor sends accurate & fast outdoor temperature and humidity measurements with its 433MHz frequency. Weather resistant case and battery powered. Note: Mount the sensor on a North-facing wall or a well-shaded location. Direct sunlight will make the temperature read high. Recommended: 6 to 18 inches below eaves or placed under deck rail is preferred. We recommend mounting outdoor sensor vertically to drain any moisture. The maximum wireless transmission range to the weather station is over 330 feet (100 meters) in open air, not including walls or floors.