The WM-300 is a comprehensive instrument for agriculture, forestry, emergency management and other industry professionals. In addition to relative humidity, the unit measures dew point, wet bulb, Delta T, temperature & wind chill. It has a USA-made fluxgate compass for precise digital wind direction measurement, and it can also be used to calculate crosswind, head/tail wind readings. Unlike a traditional compass, the WM-300 reads when held vertically and can be used to take a bearing on a distant landmark or reference location. The WM-300 includes the Accuweather patented Comfort Index, which is the effect of temperature, wind speed, relative humidity and sun intensity on the human body for a superior human based reference to Heat Index. WM-300 can be tripod-mounted and accommodates the Model SM-WT wind tunnel accessory for very precise measurements. All WindMates are designed with a wind speed accuracy of better than +/- 3% and have a 2-Year warranty.