Somehow I am puzzled that this does not have audio, would be really helpful to know the spelling
Check it here: https://forvo.com/word/lượng_mưa/
From Chinese 量 liàng (Cantonese loeng6).
Is this any precipitation or rain specifically?
I asked my native-speaking vietnamese father-in-law; he said "lượng mưa" sounds strange, but thinks it means more like rainfall or amount of rain in an area. He said normally, people just say "mưa" for rain.
I'm curious too as "precipitation" isn't a word used that frequently in English.