Accuracy: Wind, ±3%; Relative Humidity, ±3%; Temperature/Wind Chill, ±1.8°F; Dewpoint, ±3.6°F; Comfort Index, ±3.6°F; Digital Compass, ±2° with proper calibration (typical), ±6° in extreme northern and southern latitudes. Range: Wind, 0.8 to 89 mph; Relative Humidity, 5.0% to 95.0% non-condensing; Temperature, -20.0°F to 158°F; Wind Chill, -50.0°F to 50.0°F; Dewpoint, -20.0°F to 158.0°F; Comfort Index, 70.0°F to 130.0°F; Digital Compass, 0 to 360°. Optional Units: Wind, Knots, mph, kph, m/sec, ft/min, Beaufort Scale; Relative Humidity, %RH; Temperature/Wind Chill/Dewpoint/Comfort Index, °F or °C; Digital Compass, Degree and 16 directions. Auto Shutdown: After 5 minutes. Power: 1 CR2032 Lithium battery.