the calm before the storm

US /ðə kɑːm bɪˈfɔːr ðə stɔːrm/
UK /ðə kɑːm bɪˈfɔːr ðə stɔːrm/
"the calm before the storm" picture
1.

暴風雨前的平靜

a period of unusual quiet or inactivity before a period of great activity, excitement, or trouble

:
Everyone was quiet, but I knew it was just the calm before the storm.
所有人都很安靜,但我知道那只是暴風雨前的平靜
The quiet morning was the calm before the storm of the busy workday.
寧靜的早晨是繁忙工作日暴風雨前的平靜