Wind Direction at O MPH?

Our second grade class is checking the weather each day. We would like to know when the wind speed is 0 mph how can there be a wind direction? Thank you, Mrs Masteller's 2nd Grade Class

MIKE MOSS SAYS:  Actually, there can't be a direction if the wind speed is truly zero. That would mean the air isn't moving at all, and if it isn't moving, it can't be going in a particular direction. Usually, in weather observations, a wind speed that rounds off to zero is reported as "Calm," and that way no direction is given. However, it is possible for wind speed to be very slight, say one third of a mile per hour. If you are looking at a wind readout from an anemometer and wind vane, the anemometer may not be sensitive enough to record the wind speed, and may show zero, while the wind vane is able to align itself with the very slight wind and show what direction it is blowing from. Also, even when the wind is truly calm (0 mph), the wind vane may continue to show the last direction the wind blew, even if it has stopped completely since then.