Abstract: A portable hand-held vane anemometer is disclosed in which a modular vane assembly is removably mounted within the casing of the instrument. Within the modular vane assembly is a rotatably mounted impeller shaft. The impeller assembly preferably can be removed and inserted into a cavity of the anemometer. Consequently, if the impeller, bearings or other components of the impeller assembly should become damaged, the modular impeller assembly can be quickly and easily replaced. The vane anemometer of this invention may also measure temperature dependent environmental parameters and may also have the ability to measure these parameters relatively quickly and accurately when moving from one thermal mass to another thermal mass. These environmental parameters may include ambient temperature, wind chill, humidity and heat index. In order to determine these parameters, the vane anemometer may have a temperature probe and a humidity sensor that are disposed external to the casing.