From Glossary of Meteorology


An instrument showing qualitatively whether the air is dry or damp, usually by the change in appearance or dimensions of some substance (
see chemical hygrometer).

Hygroscopes are frequently used as home weather predictors, for example, "weather houses" in which the appearance of the "old man" or the "old woman" is determined by the twisting and untwisting of a piece of catgut in response to changes of humidity.

Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact [email protected]. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.