Lesson 2 - Humidity is the measure of the amount of water vapor in the air. You are more likely to feel the humidity on a hot, summer day because warm air can hold more water vapor than cool air. When air has as much water vapor in it as it can hold, the air is saturated. Scientists measure the humidity by describing how many grams of water are found in a cubic meter of air, or g/m.
Relative humidity measures the amount of water vapor in the air as a percentage of the maximum amount that saturated air can hold at a given temperature.
When the air reaches 100% relative humidity, it is saturated and cannot hold any more water vapor. At this point, it will rain or condensation will form. This is called the dew point. The dew point temperature is the temperature at which air is saturated.
Both relative humidity and dew point measure how much water vapor is in the atmosphere. Relative humidity, however, is temperature-dependent while dew point is not. The dew point is simply a measure of how much moisture is in the air at a given time. The higher the dew point, the muggier it will feel. You can use dew point as a forecasting tool to show if it is going to be hot and sticky or dry and pleasant.
