Wikipedia is too complicated for me
In: Chemistry
I’ve had dewpoint explained to me at least five times and understand it when it’s explained, I never seem to remember it afterward.
Not that that helps you or anything.
The amount of water in the air (“humidity” on the weather report) is measured as a percentage, but how much water the air can hold varies by temperature. Warm air can hold more, cold air can hold less. If the temperature goes up but the amount of water in the air stays the same, the humidity percentage goes down. If it cools, the humidity percentage goes up.
“Dew point” is the temperature where humidity will exceed 100%. Which can’t happen.. instead what actually happens is water starts appearing on things as it’s forced out of the air when humidity goes over 100%. This is why your car might be wet in the morning even though it didn’t rain last night.
Why should you care? Well, if you want things to stay dry, don’t let them get cooled below the dew point. If you have clothes hanging on an outdoor clothesline to dry, the temperature is 70 degrees and the dew point is 68… maybe bring them in now if it’s getting colder. If you have equipment that could be damaged by getting wet, maybe it needs to be heated to avoid this or otherwise brought inside.
Warmer air can hold more water.
So if the temperature is 70 but the dew point is 50 it means that the temperature could cool to 50 degrees before there is condensation or fog , at 50 the humidity reaches 100% and if the air cools more it has to release the water in the form of rain or dew or rain.
In the end its just a way to say how muggy it is, the dew point will always be lower or equal to the current temp, The higher the dew point the more muggy it will feel
At lower temperatures high humidity might not be felt , if its 40 degrees out and 90% humanity it might not feel humid because its chilly
If its 100 degrees out and 90% humanity well its going to feel much more humid
Relative humidity is a calculation. Relative humidity does not mean anything unless you know the temperature and how to reverse the calculation.
The amount of water there is in the air is much better represented by a value known as absolute humidity. This value is expressed as grams of water vapor per cubic meter of air. If we watch a weather report, we never see absolute humidity. Dewpoint however happens to be the best representation of absolute humidity.
Why does this matter? 50% relative humidity can be either absurdly dry or absurdly humid depending on the temperature. A dewpoint of 50F however is always going to be comfortable air. Anything lower than 40F is going to be very dry, 60F starts to feel humid, 70F is very humid, and 80F is oppressively humid.
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