Definition: When there is a general lack of air movement, the area is said to be calm. To determine if there is a calm, you can observe smoke rising through the air. When there is no slant to the smoke, it is calm. In other words, the smoke rises straight up into the air. This is indicative of a rating of 0 on the Beaufort wind scale. This usually means winds of less than 1 mile per hour.
Also Known As: Flat calm