You can use the calm before the storm to refer to a quiet period in which there is little or no activity, before a period in which there is a lot of trouble or intense activity
To deliver from agitation or excitement; to still or soothe, as the mind or passions
If someone says that a place is calm, they mean that it is free from fighting or public disorder, when trouble has recently occurred there or had been expected. The city of Sarajevo appears relatively calm today. = peaceful Calm is also a noun. Community and church leaders have appealed for calm and no retaliation
Freedom from motion, agitation, or disturbance; a cessation or absence of that which causes motion or disturbance, as of winds or waves; tranquility; stillness; quiet; serenity
Atmospheric conditions devoid of wind or any other air motion In oceanic terms, it is the apparent absence of motion of the water surface when there is no wind or swell