What's the dew point and humidity mean?

Question

I hear it on the news everynight but I don't understand it.

Answer 1

The dewpoint is the temperature at which the air would need to be cooled, without adding or subtracting any water vapor, such that it would become saturated, i.e. have a relative humidity of 100%.  Humidity is simply the presence of water vapor in the air.  Relative humidity is the amount of water vapor in the air expressed as a percent of how much water vapor that air can contain.  The warmer the air, the more water vapor it can hold.  This is why relative humidities typically fall during the day, and climb during the night.

Answer 2

The amount of water  in the air. ....High humidity is very difficult for heart and lung patients.

Answer 3

Put simply, humidity (relative humidity) is the percentage of moisture suspended in the air relative to how much moisture it can hold.  So, if the humidity is 60% it means the air can hold 40% more before reaching its saturation point at which it can hold no more.

Dew Point is the temperature a volume of air must be lowered to before its suspended moisture become visible.   If the temperature is 70 degrees and the dew point is 64 degrees, that means if you took the air and lowered it 6 degrees you would see water vapor form. If you look up on that day and see clouds, the bottom of the cloud is where the air aloft is 6 degrees cooler.

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Answer 4

In addition to all that, the closer the dew point is to the temperature, the more humidity there is. Usually in the summer, a dew point above 65 is high. Below 60 is low, especially for the South. Once the dew point gets above 70, the air just feels horrible. I've even seen it climb to 80, which just feels disgusting. The higher the dew point, the higher the heat index in the summer. The dew point can never rise above the air temperature because otherwise the humidity would be above 100% which is not possible.

Answer 5

The dewpoint is the temperature to which a given parcel of air must be cooled, at constant barometric pressure, for water vapor to condense into water. The condensed water is called dew. The dewpoint is a saturation point.

Humidity is a measure of the amount of water vapour in the air.

High humidity means that there is a lot of water vapour in the air, and low humidity means there is a little.