。
Last night got terribly cold.
Literal
Last-night [topic-は] terribly cool-down-[past-えた].
冷える ('to get cold, cool down') — distinct from 寒い ('to be cold' as an adjective) — captures the process of becoming cold, as weather does. ひどく is the adverbial form of the i-adjective ひどい ('terrible, severe'), here used as an intensifier — 'severely, terribly.' A compact weather complaint.