brass monkey

Adjective

idiomatic not-comparable of the weather

(idiomatic, of the weather) Very cold.

Japanese Meaning

極めて寒い天候、非常に冷たい状態を指す慣用表現

The hikers weren't prepared for brass monkey weather on the summit.

その登山者たちは山頂の凍えるほどの天気に備えていませんでした。

Sense（1）

(idiomatic, of the weather) Very cold.

It's brass monkey weather today, isn't it?