When is the wind considered to be calm?

The wind is considered to be calm when there is no motion of the air detected. This means that there are no observable breezes or gusts moving through the environment. In aviation and meteorological terms, a lack of air movement is essential for determining calm conditions, which can significantly affect flight operations, takeoff, landing, and overall flight safety.

Other options refer to wind conditions that do not meet the strict definition of calm. A light breeze, for example, indicates that there is some air movement, which disqualifies it from being labeled as calm. Gusts under a certain threshold might suggest low wind activity, but they still indicate some level of air motion that also does not meet the calm criteria. Irregular wind patterns imply variability in wind speed or direction, further supporting that calm conditions are absent. Thus, the most accurate criterion for calm wind is the complete absence of air motion.