An average of three measurements per month of upper atmosphere winds and temperatures was made during the period July 21, 1950 through May 31, 1951 by means of acoustical propagation studies. Field operations were centered in Wray, Colorado (40° N. lat, 102° W. long) and extended radially 200 km. A variation in azimuth and distance from sound source to recorder positions permitted the separation of wind and temperature components of the observed upper atmosphere sonic velocity gradients. It was found that upper winds were generally westerly and of large magnitude during the winter (autumnal to vernal equinox) and easterly and of small magnitude during the summer, with wide fluctuations during the equinoctial periods. Short‐term fluctuations in the wind vector were observed to be of the same order of magnitude as the vector itself. The short‐term fluctuation is now well established. A doubly‐periodic annual variation in temperature was observed above 25‐km altitude, with mean value in agreement with accepted NACA values.