Gnomish
uch
noun. rain
noss
noun. rain
noth
noun. rain
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun for “rain” in the Gnomish Lexicon of the 1910s derived from primitive ᴱ✶ukko (GL/74), probably based on the early root ᴱ√UQU “wet” which had derivatives like ᴱQ. ukku “rainbow” (QL/98).