Abstract: An unmanned aerial system (UAS) adapted to measure one or more atmospheric conditions has a frame and a plurality of motorized rotors suspended on arms extending outward from the frame. The UAS further includes a flight control module that includes a computer programmable flight control board and a sensor package that has an air sampling scoop, a first sensor positioned inside the air sampling scoop, and a ducted fan inside the air sampling scoop. The ducted fan is configured to draw air through the air sampling scoop in contact with the first sensor. The ducted fan can be configured to operate only when the UAS is above a predetermined altitude. The UAS may also be configured to operate in a “wind vane” mode in which wind speed and direction is determined based on the pitch and heading of the UAS.