A noun for “rain” in Late Notes on Verbs from 1969 given as {ulla >>} ulo in the phrase ulo úva “rain (unwelcome) is coming”, clearly related to the impersonal verb ul- “to rain” appearing in its future form on the same page: uluva “it will rain” (PE22/167).
Conceptual Development: In the Qenya Lexicon of the 1910s, the noun for “rain” was ᴱQ. úqil, likewise related to the contemporaneous verb ᴱQ. uqin “it rains” (QL/98).
lussa- vb. "to whisper" (SLUS/SRUS). Since Tolkien eventually decided that roots in sl- yield Quenya words in hl- (though this was pronounced l- in late Exilic Quenya), it may be that the spelling *hlussa- is to be preferred.