Leonardo da Vinci built crude hygrometers in the 1400s. Earlier Hygrometers have been traced back to Nicholas Cryfts, from Cues near Moselle in around 1450.

In 1663 Robert Hook used the beard of a wild oat to measure humidity. The beard is a tiny spiral that unwinds as conditions become more humid. Later catgut was used instead of oat beards. This was a mechanical hygrometers, based on the principle that organic substances contract and expand in response to the relative humidity. The contraction and expansion moves a needle gauge.

In 1783, Swiss physicist and geologist, Horace Bénédict de Saussure built the first hygrometer using a human hair to measure humidity. (see picture)

The best known type of hygrometer is the "dry and wet-bulb psychrometer", best described as two mercury thermometers, one with a wetted base, one with a dry base. The water from the wet base evaporates and absorbs heat causing the thermometer reading to drop. Using a calculation table, the reading from the dry thermometer and the reading drop from the wet thermometer are used to determine the relative humidity.

One early version of a wet and dry hygrometer was made by J.F. Daniell in 1820. He used a "U" shaped glass tube filled with ether. At the end of the tubes are two bulbs, one painted black and one covered with silk. Inside each side of the tube is a thermometer. Ether is the dropped on the silk covered bulb and its evaporation has a cooling effect. Noting the temperature at which dew formed on the black bulb established the Dew-point of the air, from which the humidity of the air could be calculated.