YOU SAID:

it's getting cold down here underneath the weather

INTO JAPANESE

ここは天気の下で寒くなってきています

BACK INTO ENGLISH

It's getting cold here under the weather

INTO JAPANESE

天気が悪いとここは寒くなってきます

BACK INTO ENGLISH

It gets cold here when the weather is bad

INTO JAPANESE

天気が悪いとここは寒くなります

BACK INTO ENGLISH

It gets cold here when the weather is bad