[Avodah] Mention of rain in Shavuos piyyut

[via Avodah]

One of the piyyutim on Shavuos, intended to be recited in birchas
gevuros in chazaras ha-Sha"tz (it's in the machzor), mentions rain --
either geshem or mattar. I I thought that I saw the issue raised in by
Rav Sternbuch in Mo'adim U-Zmanim but I have searched unsuccessfully
there even for the question, let alone an answer. If anyone has a source
that discusses this issue, I'd be grateful for the information.

Noach Witty