This is a great question. Back in the day it was common practice to give the relative humidity, or how close the atmosphere is to saturation. There are problems with relative humidity, though. The biggest being that it is relative.... Relative to the heat and moisture content of the air. For example:

A temperature of 66 with a dew point of 58 (comfortable range) would yield a relative humidity of 75%.

A temperature of 83 with a dew point of 68 (uncomfortable) would yield a relative humidity of 61%

You see, the percentage really does not do a good job of letting you know if it is humid, or not. That is why we use the dew point. The dew point is the temperature at which moisture will condense. The more moisture in the air, the easier it is to condense, so it will condense at a higher temperature. Therefore, the higher the number, the more "muggy" it will be.

Here is the Storm Team's chart for reading dew point temperatures:

Ray Petelin,
WSEE Storm Team Meteorologist