A hygrometer is used to measure relative humidity. A wet bulb and a dry bulb thermometer are used in a hygrometer. The difference in the temperature readings on these two thermometers helps us to determine the relative humidity. Humidity is the amount of water vapor in the air. Humid air has a lot of moisture in it. The relative humidity reading tells us how uncomfortable we may feel on a summer day.

We made our own hygrometer with an orange juice carton and two thermometers.