the calm before the storm

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

暴风雨前的平静

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.
所有人都很安静,但我知道那只是暴风雨前的平静
The quiet morning was the calm before the storm of the busy workday.
宁静的早晨是繁忙工作日暴风雨前的平静