Minimum wind speed: 1.3 mph (1.2 knots, 2.2 km/h, 0.6 m/s, or 118 fpm). Maximum wind speed: 89.5 mph (77.8 knots, 144 km/h, 40 m/s, or 7,875 fpm). Wind speed accuracy: ±3%. Update: 1 second. Temperature, wind chill, heat stress, and dew point range: -20°F to +158°F (-29°C to +70°C). Temperature, wind chill, heat stress, and dew point accuracy: ±0.9°F (±0.5°C). Temperature resolution: ±0.1°F (±0.1°C). Wind chill factor resolution: ±1°C. Relative humidity range: 5% to 95%. Relative humidity accuracy: ±3% from 5% to 95%. Barometric pressure range: 870.0 hPa to 1,080.0 hPa (25.70 inHg to 31.90 inHg). Barometric pressure accuracy: ±3hPa. Altitude range: -1,500 ft. to 30,000 ft. (-500 m to 9,000 m). Altitude accuracy: ±30 meters (at standard atmospheric conditions). Operating temperature: 5°F to +122°F (-15°C to +50°C). Storage temperature range: -4°F to +176°F (-20°C to +80°C). Impeller: 1˝ diameter, sapphire bearings, lightweight. Temperature sensor: hermetically sealed precision thermistor. Humidity sensor: solid state silicon capacitive sensor. Pressure sensor: monolithic silicon piezoreisitive sensor. Display: reflective backlit LCD. Sealing: electronics enclosure IP67 water resistant to 3 ft. Floats. Battery: user-replaceable CR2032 coin cell battery (included) with a typical life of 300 hours. Dimensions: 4.8˝ x 1.9˝ x 1.1˝.