Relative humidity is the amount of water vapor actually in the air divided by the amount of water vapor for the air to be saturated. This is assuming the temperature and pressure do not change. Relative humidity is stated as a percentage.
The closer relative humidity gets to 100 percent, the more likely it is that clouds form.
Dew point is the temperature to which air must be cooled to become saturated with water vapor.
The closer air temperature gets to the dew point, the more likely it is that clouds form.
Fronts are narrow zones between two air masses. The air masses have different temperatures, humidity, or both. Clouds and precipitation often form along a front.
