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SESK: Stuff Everyone Should Know · sesk.info/aero-relative-humidity

Relative humidity of 65 percent means what?

The air holds 65 percent of the water vapor it could hold at that temperature.

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  1. The air holds 65 percent of its maximum water vapor ✔
  2. 65 percent of the air is water
  3. It will rain 65 percent of the day

Why: Relative humidity compares how much moisture is in the air with the most it could hold at that temperature. Warm air can hold more water than cold air.

Huh, didn't know that: Air at 20 degrees C can hold almost twice as much water as air at 10 degrees C.

The dad joke
Why was the humid day so tired? It was carrying too much water.
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References

Answer: The air holds 65 percent of its maximum water vapor. Relative humidity compares how much moisture is in the air with the most it could hold at that temperature. Warm air can hold more water than cold air.

  1. FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 12 Weather Theory www.faa.gov/regulations_policies/handbooks_manuals/aviation/faa-h-8083-25c.pdf
    the air is holding 65 percent of the total amount of moisture that it is capable of holding
    Checked 2026-10-10.

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