What is the difference between "Humidity" and "Dew Point"?

Question

I know they both have to do with the amount of water in the air, but I suspect that they are different readings, and pertain to different conditions.

Answer 1

Yes, humidity is simply the amount of water vapor present in the air. Relative humidity is the amount of water vapor in the air RELATIVE to how much the air can hold (expressed as a percent).

The dewpoint is the temperature that the air would have to be cooled to attain saturation (100% relative humidity) without changing the amount of water vapor in that air.

Answer 2

Dew Point vs. Humidity
The dew point is the temperature the air needs to be cooled to in order to achieve a relative humidity (RH) of 100%. At this point the air cannot hold anymore water in the gas form. If the air were to be cooled even more, water vapor would have to come out of the atmosphere in the liquid form, usually as fog or precpitation.

The higher the dew point rises, the greater the amount of moisture in the air. This directly effects how "comfortable" it will feel outside. Many times, relative humidity can be misleading. For example, a temperature of 30 and a dew point of 30 will give you a relative humidity of 100%, but a temperature of 80 and a dew point of 60 will only give you a relative humidity of 50%. It would feel much more "humid" on the 80 degree day with 50% relative humidity than on the 30 degree day with a 100% relative humidity. This is because of the higher dew point.

So if you want a real judge of just how "dry" or "humid" it will feel outside, look at the dew point instead of the RH. The higher the dew point, the muggier it will feel.

http://www.crh.noaa.gov/arx/heatindex.php

Answer 3

Dew point temperature is the temperature at which the air becomes saturated with moisture.If you bring down the temperature below the dew point, condensation of the water vapour into water will occur.
Humidity generally denotes Relative humidity which gives the percentage of moisture in the air for a particular temperature.

Answer 4

Simply stated Humidity is the amount of moisture in the air and Dew point is the temperature at which moisture forms usually at ground level.

Answer 5

Absolute Humidity = Actual amount of water vapor it the air (i.e. actual amout of water in a liter of air)
Relative Humidity = Amount of water vapor in the air vs. the amount it can hold at a given temperature. (i.e. at 50% humidity, there is half the amount of water in the air relative to the amount that the air can hold)

Dew Point = The temperature at which water vapor will turn to liquid water. (i.e. it's currently 85deg, if the dew point is 80deg, you will get dew or rain if the temp drops 5 deg.)

Answer 6

Humidity is measured as a percentage of moisture in the air. Dew point is the temperature that the air is saturated with moisture and dew/rain forms and falls.

Answer 7

Humidity is a measure of water vapor present in the air.

Dew point is the temperature at which the moisture in the air condenses into a liquid, not the freezing point as previously stated by kelley belly.

Answer 8

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Answer 9

Humidity deals with how much water vapor is present in the air, and dew point deals with thet water vapor's freezing point. It's the temperature at which the water vapor freezes, like you see sometimes on the grass or your car.