What does a wind vane measure?

A wind vane is an instrument specifically designed to indicate the direction from which the wind is blowing. It typically consists of a rotating arrow or blade mounted on a vertical shaft. As the wind blows, the vane rotates until it aligns with the wind direction, allowing the user to determine where the wind is coming from.

Understanding the function of a wind vane is crucial for meteorological observations because wind direction can significantly affect weather patterns and conditions. For example, winds coming from the ocean may bring moisture, while winds from the land might be drier. Because of its specific design and purpose, the wind vane does not measure wind speed, humidity, or temperature, which are assessed by other instruments such as an anemometer, hygrometer, and thermometer, respectively.