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Taking science by storm: feeling foggy

Ice fog near the town of Divide
Posted at 1:54 PM, Apr 09, 2020
and last updated 2020-04-10 11:15:01-04

Fog is essentially a cloud on the ground! All you need is for the air near the ground to become completely saturated with water vapor, and that can lead to fog formation.

Definition: The dewpoint is the temperature to which the air must be cooled in order for that air to be saturated.

Definition: Relative humidity is a measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature.

When air is saturated, that means the relative humidity is at 100%. This also means that the air temperature and the dewpoint are the same.

Use this calculator to explore the relationship between, temperature, dewpoint, and relative humidity.

This experiment was adapted from

Time: 10-15 min


  • Small glass jar (can hold about 10-12 oz.)
  • hot water
  • strainer
  • ice cubes (about 5-7)


  1. Heat the water to near boiling with a kettle, coffee maker, pot on stove, etc.
  2. Pour hot water into jar until full
  3. Wait 1 minute
  4. While waiting, add the ice cubes to the strainer
  5. Using oven mitts, carefully empty half the water from the jar
  6. Place strainer on top of jar
  7. Observe the steam fog! Try illuminating the jar with a flashlight to enhance the visual.

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