the calm before the storm

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

a calmaria antes da tempestade

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.
Todos estavam quietos, mas eu sabia que era apenas a calmaria antes da tempestade.
The quiet morning was the calm before the storm of the busy workday.
A manhã tranquila era a calmaria antes da tempestade do dia de trabalho agitado.