The radar-derived winds (60-110 km) at Saskatoon (52¿N, 107¿W, 61¿ geomagnetic) for the summer and winter months of 1982/1983 are separated into categories according to the daily planetary magnetic index Ap: quiet 19(D). The data yield, which is directly related to the scatter of radar pulses from the middle atmosphere, is much enhanced for both the moderate and disturbed categories during nighttime and early morning hours. The seasonal and height variations of radar scatter are related to particle precipitation characteristics. Above 90 km there are also small changes in the mean winds and in the amplitudes of both 24- and 12-hour tidal oscillations (10%) due to variations in magnetic activity. The small phase changes identified for both tidal oscillations show interannual variation and are most likely due to data selection effects. The wind data are further separated according to the amplitudes of the daily tides (greater or less than 20 m/s). The yield of radar data is significantly greater when the tides are large for each season and disturbance category. This effect is related to the dynamic stability of the atmosphere and the increase of turbulence and hence radar scatter due to the large tidal amplitude. ¿ American Geophysical Union 1991