Often the decorative accent atop the peak of a barn roof, weathervanes add rustic charm while serving as a tool for gardeners wishing to determine the wind's direction. Oriented and marked according to the cardinal directions of north, south, east and west, the vane has one swiveling arm that rotates according to the wind's origin. The pointed arrow of the swiveling arm always points into the wind, revealing the direction from which the wind originates. Thus, a weathervane that points to the "N" shows that the wind is blowing (starting) from the north and moving to the south.
Look at the weathervane and note if there are any cardinal direction markers. There may only be one, which likely will be the letter "N" for north, or it might also have the other markers--"S" for south, "E" for east and "W" for west. These markers are stationary and point to the cardinal directions.
Stand still for 10 to 30 seconds and watch for movement of the vane's wind arrow. This movable and swiveling arm of the weathervane traditionally looks like an arrow with a pointed arrowhead and tail fin or feather. Once seen, note which end of the wind arrow is the pointed tip and which is the tail from your vantage point.
Read the direction of the wind arrow on the weathervane. The pointed tip of the wind arrow points into the wind. Based on the directional markers on the vane, deduct where the wind arrow points according to the four cardinal directions. If the wind arrow is pointing outward between the "E" and "S" directional markers, the wind is coming from the southeast. In other words, the wind originates from the southeast and goes to the northwest.
Assume that a quickly rotating or spinning wind arrow on a weathervane indicates variable winds, violent eddies or changing air flow. A resting wind arrow means no wind or a very faint wind that is too light for the wind arrow to indicate.