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SESK: Stuff Everyone Should Know · sesk.info/comm-cloud-base-temperature-dewpoint

Surface temperature is 85 F and the dew point is 71 F. About how high is the cloud base?

About 3,200 feet above the ground.

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  1. About 1,400 feet
  2. About 6,100 feet
  3. About 3,200 feet ✔

Why: Lifted air's temperature and dew point close together by 4.4 F per 1,000 feet. The gap here is 14 F, and 14 divided by 4.4 is about 3.2, so clouds form near 3,200 feet.

Huh, didn't know that: As unsaturated air is lifted, it cools 5.4 F per 1,000 feet while the dew point drops about 1 F per 1,000 feet.

The dad joke
Why did the cloud base need a calculator? Its temperature and dew point kept converging.
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References

Answer: About 3,200 feet. Lifted air's temperature and dew point close together by 4.4 F per 1,000 feet. The gap here is 14 F, and 14 divided by 4.4 is about 3.2, so clouds form near 3,200 feet.

  1. PHAK ch 12, Weather Theory (FAA-H-8083-25C) www.faa.gov/sites/faa.gov/files/14_phak_ch12.pdf
    With an outside air temperature (OAT) of 85 °F at the surface and dew point at the surface of 71 °F
    Checked 2026-10-11.
  2. PHAK ch 12, Weather Theory (FAA-H-8083-25C) www.faa.gov/sites/faa.gov/files/14_phak_ch12.pdf
    The height of the cloud base is 3,180 feet AGL.
    Checked 2026-10-11.
  3. PHAK ch 12, Weather Theory (FAA-H-8083-25C) www.faa.gov/sites/faa.gov/files/14_phak_ch12.pdf
    the dew point temperature decreases at a rate of 1 °F per 1,000 feet.
    Checked 2026-10-11.

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