Weather Instruments

Anemometer - Measures wind velocity. Made of three or four hollow hemispheres that catch wind and rotate. The wind velocity can then be calculated from the rotation.
Barometer - Measures atmospheric pressure.
Hygrometer - Measures the moisture content/humidity of a gas.
Rain Gauge - Measures how much rain has fallen.
Thermometer - Measures the temperature. Thermometers work by using materials which expand and contract with changing temperatures.
Weather Vane - Shows which direction the wind is blowing.