How does an anemometer measure wind speed?

Meteorologists use a few different types of anemometers.

One type of anemometer is a hot-wire anemometer. The hot-wire anemometer measures the wind speed based on variations in temperature or electric resistance of a metal wire. As the wind speed increases more energy is used to keep the metal wire at a preset temperature. Wind speed is determined by measuring the electrical consumption of the wire. This device is not typically used for official National Weather Service wind measurement.

Another type of anemometer and probably more familiar type is a rotation anemometer. This device measures wind speed based on the rotation of a sensing element such as a propeller or spinning cups. As wind speed increases the anemometer will rotate faster. Portable versions of this anemometer are also available.