Types

• Hygrometers come in many varieties but all perform the same function of measuring humidity levels. The mason and whirling type hygrometers are typical examples of manual meters, while the digital hygrometer is a more accurate device for use in small areas. Many weather enthusiasts choose a digital hygrometer over the other varieties because of its ease in handling and accuracy in measurements.
  
  

Prediction

• A hygrometer is an important component in predicting the weather. However, you cannot predict the weather with only a hydrometer. To make a full and accurate prediction, you will require a weather map of the area, which will have information on the general weather trend for the past few years. Next, you will need a wind speed indicator or an anemometer and an air pressure indicator or a barometer. With these four items and a general knowledge on the average rainfall of the locale, you are all set to predict the weather.
  
  

Variables

• To understand how the hygrometer is used in weather prediction, first it is necessary to understand the various variables in the weather equation. Humidity, pressure, temperature and air speed are the four variables involved. Without information or knowledge on all of these variables, it is quite difficult to predict the weather. Air pressure, put in non-technical language, is the density of air in a particular region compared with its surroundings. A low-pressure region is where the air is rising up and air from surrounding high-pressure region is rushing in. Therefore, rain and snow are always seen in low-pressure regions.
  
  

Importance of Air Speed

• The air speed will tell you about the probability of rain happening. The faster the air flows, the lower the pressure will be, increasing the chance of a downpour. The temperature is the variable, which as everybody knows decides whether there will be snow or rain or neither.
  
  

Importance of Humidity

• Humidity refers to the concentration of water vapors in the air. The more the saturation of the air, the greater the chance of rainfall. Notice that whenever the humidity of your place is at 70 percent or above, it will receive some amount of rainfall. This is because humidity plays a major role in determining the probability of rain and snow. A hygrometer allows you to measure the humidity of your place, and--coupled with the other measurements--you can predict the weather of your locality. This is also how a hygrometer is used by weather stations to predict weather all over the world.